Add a status for a layer indicating it should not be updated. I don't
expect this to be widely used (and is only settable from the admin
interface) but would be useful if you have a legacy sub-layer that you
want to prevent from being visible on certain branches - it will prevent
the update script from doing anything with the layer and thus avoid
branch records from being auto-created on branches where you've deleted
it.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
