Add Flash-Friendly File System (f2fs) support.

Change-Id: If46bf7329a7453122a4379f9bc41cf9553426e74
vold: allow pre-configured device pairs to switch mountpoints

By setting persistent system properties
 persist.sys.vold.switchexternal=1
 persist.sys.vold.switchablepair=sdcard0,sdcard1 (for example)
two non-emulated extended storage devices can swap between primary
and secondary storage.

This commit is heavily inspired by Rick Fernie and Ricardo Cerqueira's
"vold: Allow pre-configured device pairs to switch mountpoints"
[http://review.cyanogenmod.org/12764] but adapted to CM's newer vold.

Change-Id: I2be5d4799c2d8f04a535096ac4c7619849f1f84a
Merge pull request #1 from iiD4x/kitkat

needed for STE to avoid low data partition
Add exfat/ntfs support for modules or static mode.
if you cannot write to partitions, it could be you miss SE permissions

Change-Id: I3d460174da140ae3b099ceed0922f8287dd80676