tidied up confusion between orbital regions and ocular regions

UBERON:0001697 has been relabeled from 'orbital region' to 'orbit of skull' to
make its nature as part of the skeleton clear.

The overall partonomy is

```
 ocular region (subdivision of face)
   orbit of skull (skeletal)
   eyebrow
   eye
     eyeball
     eyelid
     lacrimal gland
```

Addresses issue #607
Also related to #462
glands are never parts of the skeletal system.
Fixes issue #607
and prevents further issues of this sort