Comment-obsolete-code dev branch

[marcustyphoon]

The Github history of each one of the files in this extension package is a monument to over a decade of community development, and I think that's kind of beautiful. On the other hand, shipping a massive amount of unused, obsolete javascript code that's up to a decade old is, like, you know... bad. (For review, for performance, etc.)

This implements a small tweak to the extension load code that'll make a commented-out file mostly a no-op. This facilitates the use of block comments to relatively easily remove large swathes of javascript from our reviewable, executable codebase while preserving the per-line git history and making re-enabling commented code (e.g. to update it or to revert an accidental comment) extremely easy.

(I have not at time of writing gone through to see which extensions should be commented and which are still usable on legacy pages and should thus stay; I don't think our documentation or the colors applied in xkit_preferences.css are entirely without error.)