Themes: Handle processing themes in separate thread

If themes are being processed and the user attempts to apply a theme
they will be forced to wait for themes to finish processing before
the theme is applied.  This patch moves processing of theme resources
into a separate handler/thread.

Change-Id: Ib30a1be75915364c2867df04d63700be63c9f2c5
Merge remote-tracking branch 'cyan/cm-11.0' into cm-11.0