Storage Settings: Allow user to trigger a volume rescan

This change allows to trigger a rescan of a volume with the next restrictions:
- Internal volumes if they are emulates
- Primary volumes
- Non-Removable volumes

Ported from: http://review.cyanogenmod.org/44586

Change-Id: I7e75a324938d8081fd715f702d50f1fdceabd96d

Conflicts:
	res/values/cm_strings.xml
Revert "Revert "Navigation bar buttons customization""

This reverts commit 1b56304c9d738149bddadedaaa1375ed4a7d97df.
Use holo alert drawable for nav bar editor