MR process: Maintenance REPL improvements

[jonathanolson]

As noted in #132, there are essentially two improvements desired:

When using the maintenance REPL in GitBash / Windows 10, TAB auto-complete and Ctrl+C do not work as expected. It would be super nice to get these working for Windows devs.

Can we add history between sessions in the maintenance REPL? It would be convenient to be able to access previously typed commands across sessions.

[jonathanolson]

Now --experimental-repl-await may be usable, so it may be possible to get rid of our custom evaluator.

In the documentation (https://nodejs.org/api/repl.html), it seems that using a custom evaluator precludes us from using the option breakEvalOnSigint (which is presumably why the Ctrl+C is exiting). This would require Node 10+, and I'm not sure if it would be compatible with grunt.

Additionally, on Windows (with Git Bash) I can't seem to get any calls to the auto-completion logic.

I'm going to leave unassigned, as I'm getting diminishing returns. @mattpen if you're interested into looking into this, I'd say go for it.

[mattpen]

I think @jessegreenberg or @zepumph discovered that the ctrl-c and tab complete work in WSL, so I think if you're seeing diminishing returns that we shouldn't worry about it getting it to work in GitBash.

[jessegreenberg]

In #139 we also discovered that Windows git bash Ctrl+V adds extra \u0016 characters that may be interfering with things.