D3FC unit test

[texodus]

Added support for Jest unit tests w/babel to the perspective-viewer-d3fc plugin, with a stolen test implementation from the D3FC PoC repo

[texodus]

@matt-hooper There were a few issues:

• babel-jest did not add support for Babel 7's babel.config.js until version 24, which caused our settings to not get picked up.
• The top-level jest config had transform: {}, and used roots instead of projects which caused the package local configs to not get picked up.
• There is a bug in jest which causes it to always ready the babel.config.js from the <rootdir> rather than the local package when using the multi-project runner, which required a custom transformer workaround.

I've also moved the test suite into integration/ and unit/ sub-directories. Let me know if this is OK to merge.

[matt-hooper]

Thanks for the PR. I will take a look and let you know how I get on.

[matt-hooper]

@texodus, I have no issue with this being merged. It will be very useful. Thanks

[texodus]

Groovy, thanks!