Remove unused hooks

These are superseded by functionality provided by other hooks and are no
longer needed.

Change-Id: Id6ea1fc927f1e990acd102a08ab3e6dc971aa4d7
Reviewed-on: http://gerrit.causes.com/35586
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: Shane da Silva <shane@causes.com>
Add ImageOptim hook

Change-Id: I87aa93345a4f320e5a414aee4f77a69b3a197032
Reviewed-on: http://gerrit.causes.com/35587
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: Shane da Silva <shane@causes.com>