This includes two larger changes, the first one being profiles now record the
editor library version they are compatible with. This allows for better control
when moving from one library version to another. The second change is to the
profile overview UI, which now only stores profiles temporarily until they have
been explicitly saved.

This change also includes a new method of retrieving the list of stylesheets
added by the selected theme, and a new alter hook for that list.
If CSS aggregation is enabled the final list of stylesheets sent to the editor
will also be aggregated/optimized if possible.

Jake Bell authored Nov 20, 2016 and Henrik Danielsson committed Nov 20, 2016

- #828718 by theunraveler, danbohea, BrightBold, jonraedeke, colinstillwell88, jennifer.chang, et al.: Fixed hard .css setting cache: how to clear the cache?

Follow-up to #2243413.

Cleans up mistake from #2018439.

James Elliott authored Sep 17, 2012 and Daniel Kudwien committed Sep 17, 2012

- #835682 by james.elliott, TwoD, Paul Lomax, JacobSingh: Fixed %t (path_to_theme()) returns wrong theme path.