obj persistence: delete objects directly by object ID

Previously, you could only delete objects from flash
if they had been initialized.  This prevented deleting
settings UAVOs for optional modules that were currently
disabled.

Now, you can delete the object from flash directly by
object ID + object instance.  This allows a user to
delete specific settings objects when in BootFault mode
even when the problem module is disabled.
obj persistence: rename UAVObjDelete to UAVObjDeleteByID
Merge pull request #349 from solidgoldbomb/directly-delete-objects

obj persistence: delete objects directly by object ID