Show cover art in spinny underneath spinny background.

This means spinny backgrounds should be partially transparent so they
can mask the art.
Add tooltips for CoverArt and StarRating widgets to list of available tooltips
Add tooltip for Bitcrusher effect
Add tooltip for Flanger effect
Address review notes for Bitcrusher & Flanger effects
Merge pull request #392 from esbrandt/tooltips

Tooltips
LateNight: Fix microphone widget not showing up in skin when configured.
Add optional <ShowCover> bool element to Spinny so skins can disable covers.  (Default to true)

Update LateNight skin with new, better-looking spinnies that show the covers.
Make SelectX elements case-insensitive.
Remove unnecessary .toLower calls

Tweak color of spinnies.
Merge pull request #391 from ywwg/spinny-cover-art

Show cover art in spinny underneath spinny background.
Code fascism.

* Fix compiler warnings in non-3rd-party code.
* Add some missing const-references.
* Eliminate cases of "if(" "( ... )" and "for(".