[ENH] Drawables: revenge of the lint

A bunch of little visual linting checks. Grouped together because none of these reall bear much review.

xhdpi drawable asset directory was missing a lot of versions
an old, low-res grayscale planet icon was doing mixed/triple duty at points in the UI
android 24-29 had a mismatched icon in notification bar
DP sizes in icons were inconsistent across DPI folders
removing a lint warning in our port of the map bubble UI (because we learned it from Google)
an errant dimens entry

wiglenet / wigle-wifi-wardriving