Revert "Advanced storage: swap primary storage for apps"

This reverts commit 8de545ff63767300626cd5efbf53259aa9b5d63f.
Revert "Advanced storage: vold swap storage paths"

This reverts commit d603e2b1885e34d448e096348420deb4346fb96f.
Advanced storage: vold swap storage paths
Advanced storage: swap primary storage for apps

Advanced storage settings patch series:
[1/4] vold: allow swapped storage paths at vold init
      http://review.cyanogenmod.org/56515
[2/4] Advanced storage: vold swap storage paths
      http://review.cyanogenmod.org/56516
[3/4] storage: allow swapping primary storage for apps
      http://review.cyanogenmod.org/56950
[4/4] Advanced storage: swap primary storage for apps
      http://review.cyanogenmod.org/56951

This adds a new preference to Advanced storage settings to swap the
primary storage path used for applications storage. Whereas the original
vold swap trick cannot be used when primary storage is emulated, this
setting can be applied to either emulated or non-emulated storage. Only
one of the two primary storage swap methods can be active at a time.

This option is currently restricted to a secondary storage device
located at /storage/sdcard1 to prevent swapping with not-so-permanent
devices like usbdisk.

The effect of this option can be verified by going to Settings > Apps
and swiping over to "ON SD CARD". The bar at the bottom of the screen
should have used/free spaces corresponding to /storage/sdcard1.

Inspiration for this storage swap method comes from Martin Meloun.

Change-Id: I5eb31735baeb8e356f94cc1b87fa9618023db8ce