Set up Vold switchable pair to allow swapping internal/external SD

Uncomment the line persist.sys.vold.switchexternal=1 in bulid prop
to use

Change-Id: Ic669d2682f9d9ee2400693d987610528fb653e7a
Add init.target for symlinks
Merge pull request #6 from STS-Dev-Team/phablet

Phablet