Reimplement subsections in Options

Reimplement subsections in Options

Now the support for sections in Options provides an API similar to
other option types.  The main thing missing (both in the old and the new
implementation) is support for an "array of structs"-kind of options,
where multiple instances of the same section could create multiple
instances of some object in the code.  That should also be possible to
add following a similar public API, but the internals need quite a bit
of generalization to make that possible.  That will be done in
subsequent changes to keep the changes smaller.

Remove now-unused name and title for an Options object.

Change-Id: Ie76e31aae2de0816b4d294ff6869606d4a2bef49