Swap /system and /data partitions

Remap the /system partition to /data, and vice-versa.

Rationale:
* Increases space available on /system, which is needed by CM11/gapps
* Reduces space on /data, but that is less of a problem (app2sd).
* This is a good time to implement the switch, as all devices need new
  recoveries for the hardware TLS changeover.

Change-Id: I79cbc399b536bbbc035a18825ee4853ef85d1db5