Run 'chattr -R -i' on ROM's folder before deletion

* SuperSU creates file with immutable attribute which prevents it
  from being deleted, because of reasons
Merge branch 'nexus7' into mine
Copy fstab.* in MultiROM::extractBootForROM()
Don't skip updater-script lines with "mount" if it's symlink creation
Merge branch 'nexus7' into mine