Removed ScorePackageManager.rename_score_package().

Use ScorePackageWrangler.rename_score_package() instead.
Updated TODO.
Cleaned up MaterialPackageManager.

Removed remaining references to user input module.
Removed Manager.remove().

Use the wrangler remove_*() methods instead.

Note that the wrangler remove_*() methods all wrap Wrangler._remove_asset().
Updated TODO.
Updated TODO.
Wrote StylesheetWrangler view tests.