Makes it easier to edit them manually directly in the registry files.
(Something end-users are of course not expected to do, but admins or hackers
may want to do.) Also guards against the possibility of the numeric values of
the opcodes being changed. I figured out how to do the mapping from symbolic
names to enum values and back without an ScDocument, turned out it was not
complicated after all.

Change-Id: I8bd97f256f7d777162c1b629bf82285544e86d70