Removing a skeleton from the object tree now removes also its terminals
Removing a skeleton from the object tree now removes also its terminals

Fixes #240. Also all missing ON DELETE CASCADES should
have been added. Fixes #81. The foreign keys should all be
correct. Fixes #82. This should also fix another issue
with that was a dublicate. Fixes #97.

fzadow/CATMAID,fzadow/CATMAID,fzadow/CATMAID,htem/CATMAID,htem/CATMAID,fzadow/CATMAID,htem/CATMAID,htem/CATMAID