Updated dependencies, added eslint, rollup, plus some fixes

[taoeffect]

This PR

• Removes the no-longer-maintained vueify and switches us from browserify to the more advanced (and more rigid) rollup
• Removes all related dependencies to vueify and browserify
• Updates many dependencies (including babel to version 7) and fixes critical npm audit warnings
• Extracts component scss out of the bundle and into a component.css file
• Adds support for dynamically lazy-loading components with import() and shows an example of how to do that with UserGroup.vue in router.js
• Moved all files in frontend/simple up one directory and placed all router links under /app URL (Move the stuff in frontend/simple up one directory #526) in order to make it easier to serve the app using third-party tools
• Significantly improves our linter by switching from standard to eslint with eslint-plugin-standard
• Deleted all the old stuff in frontend/_static
• Creates a new top-level folder called historical under which old but potentially useful code can be kept
• Updates browserslist key in package.json so that async/await do not get transformed by babel

I recommend viewing the diff with whitespace changes turned off.

TODO

• fix import of circle slider
• Try Grunt integration with rollup.watch instead of rollup.rollup! Replace rollup-plugin-serve with serve, or better yet, just keep what we currently have with grunt and run rollup via grunt / grunt-exec that didn't work out too well. So now am thinking maybe I should try with browser-sync? Or maybe just switch to webpack...? Maybe leave it all for a future PR.
• Remove all browserify related dependencies and migrate any remaining stuff to rollup (for example, by using script2ify with rollup-plugin-browserify-transform
• See if it is better to replace Grunt with npm scripts or to stick with it
• Use eslint with eslint-config-standard so that it lints .vue files (instead of using standard directly, because it doesn't support that for some reason)
• Make the SASS setup coherenet, simple and DRY
• Connect the SASS setup with the vue code so that JS has access to theme variables from the SASS
• NOTE: this is now part of issue Fix eslint and web console errors and warnings, plus verify sass support in components #525 - Verify that (1) vueify is loading the sass that's imported in Sidebar.vue, and (2) that when I removed ../../ from // @import "../../node_modules/bulma/sass/utilities/initial-variables"; (and all the other ../../node_modules), that I didn't break anything. Re-add the ../../ if I did. Choose either the grunt-sass, or better yet (so that @import can be called from components), remove grunt-sass and use the bundler's sass plugin (whatever the equivalent for vueify/rollup/webpack is)
• Create issues out of any of the above that need to be created, as well as the rollup log output below:

(!) VuePlugin plugin: <contribution v-for="contribution in fakeStore.receiving.nonMonetary">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/Contributions.vue
(!) VuePlugin plugin: <contribution v-for="contribution in fakeStore.giving.nonMonetary">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/Contributions.vue
(!) VuePlugin plugin: <voting-banner v-for="proposal in Object.values(proposals)">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/containers/Proposals.vue
(!) VuePlugin plugin: <voting v-for="proposal in groupProposals.notVoted">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/containers/Proposals.vue
(!) VuePlugin plugin: <voting v-for="proposal in groupProposals.own">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/containers/Proposals.vue
(!) VuePlugin plugin: <voting v-for="proposal in groupProposals.alreadyVoted">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/containers/Proposals.vue
(!) VuePlugin plugin: <list-item v-for="id in list.order">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/components/Chatroom/ConversationsList.vue
(!) VuePlugin plugin: <menu-item v-for="group in groupsByName">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/containers/sidebar/GroupsList.vue
(!) VuePlugin plugin: <message v-for="message in ephemeral.pendingMessages">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/components/Chatroom/ChatMain.vue
(!) VuePlugin plugin: <avatar v-for="user in founders">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.
frontend/simple/views/containers/Chatroom/ConversationGreetings.vue

[taoeffect]

OK @pieer this PR is ready for your review! 😄 🎉

Please also see the related issue that I just created: #525

[pieer]

Remove commented code?

[pieer]

Any reason why this code is going to global css now?

[taoeffect]

I will add the scoped back in, but also have added a bunch of comments about doing this properly with transitions.js (which currently has a poor implementation that isn't really being used), that's something that I hope you can improve.

[taoeffect]

Created #529 to address this.

[pieer]

All good. Great work!