Build: Add support for specifying build variant in brunch/breakfast

This little modification allows specifying build variant in brunch/breakfast commands. For example we can use "brunch i9300 user" to build user variant instead of default userdebug.

When no extra argument is given, userdebug is default.

Change-Id: I2d438209f8a14949c64baa66485c811da384d20b
fix scorpion build

Change-Id: If746970ce5b97fccfe52bd8603a1902f89d9389e
build: allow mounting by partition name through edify

With more devices migrating over to emulated storage there is a need for
increased flexibility when mounting partitions. Edify scripts currently lack
the ability to mount emmc partitions by their labels, so busybox is used
as a reliable alternative.

This allows partitions to be mounted by name while still maintaining
compatibility with older recoveries.

To use define TARGET_SETS_FSTAB in the device's make files

Change-Id: I905740dd566f451b7ac48579a85e1b39a8cfd31a
Merge branch 'android-4.4' of https://github.com/omnirom/android_build into omnirom-android-4.4

Conflicts:
	envsetup.sh