Apps in spotlight

Alright folks. Here's a PR for commentary.

This addresses both #99 and #143 - and possibly a few more I'm missing.

* Apps get ability to specify linkables. See discussion in #143 and thanks to @passcod for the initial implementation and guidance
* We're moving the `Caskroom` to fix #99 - spotlight picks up apps in `/opt/` just fine we get that for free without any fancy `linkapps`ing.
* All app links are staying symlinks. Because AppleScript made me hate my life.

Please comment and question and poke and prod here and once we all feel good we can merge!

:mag: :mag_right: :mag: :mag_right: