Overhaul the System Configuration menu - moved all Security Options to submenu

The security-related options were really spread around and this menu was
getting very overloaded (the list of Toggle Options had grown huge), so now
most of the content is actually under the new "Security Options" sub-menu.

This does make a bunch of previous instructions/docs slightly out of sync
(e.g. SCFG->System->Security Level Values should now be
SCFG->System->Security Options->Security Level Values), but I think sysops
will still find stuff just fine.

This re-org will allow me to add more options that I've wanted to but needed
better organization and structuring to do so logically and clearly.

Using the memcmp() trick to detect changes in the configuration.

No new settings/option were added in this commit.