Provide autocompletion / code-hinting for SublimeText Settings

This feels like some low-hanging fruit that would dramatically improve the user experience.  It's mega frustrating to have to flip back and forth between the user settings and the default settings, just to check the name of some setting or its allowed values, etc.

I think this is a win all around.
-alex

(this is the point at which you tell me it's existed since v2 ... heheh)