Gallery2: fix HDR crashes && fix exposure from being set.

* HDR transcoding is done on a different thread. got rid of the
stall in the transcooding step and possibliy fix race conditions.
* lock out the exposure step from being set, also fix an issue
of setting is being set by a method that is called on idle.

Change-Id: I9558558777a11cc8f6b633e397c809aa6993ceaf
Storage location configuration options

Based on d050f80 and 2bb0437 in the former Camera package

PS2: Whitespace cleanup

PS3: Fixed filmstrip preview from camera.

PS4: Check volume availability

PS5: Load the settings when either the camera opens
  or when the gallery opens

PS6: Remove unused import

PS7: Rebase

PS8: Change icon to stat_notify_sdcard, add credit for
  original sources

PS10: Code style cleanup, include icon, and add setting
  to the camcorder settings

PS11: Rebase, reword commit message

Change-Id: Ic484149f1f051aea5c5c8440bbc322e9924683a7

Conflicts:
	res/values/cm_strings.xml