Make module whitelisting setup easier

[elad661]

Currently when you want to have a module whitelist you need to type the names of the modules you want to load.

It would be awesome if instead we could show a list of installed modules and have users check the ones they want to load (using arrow keys to navigate, and enter or space to toggle selection)

[Exirel]

Related to #1471

[dgw]

Sounds related to #1507, also. Or rather, to the follow-up in which you'll add more features on the config-editing side of things.

[Exirel]

@dgw I would argue that #1588 fixes that!