Now it actually defaults to "a < b" comparison, instead of forcing you
to provide a trivial less-than comparator. Also you can pass in any
collection type that has .begin() and .end() and we'll sort it for you.
I probably would've done INI config removal in another commit, but it
fit well here because I didn't want to pledge wpath for SystemMenu if I
didn't need to.
Frankly, that's something that I think should be done: allow ConfigFile
to be used read-only.
This will allow us to run the system menu as any user. It will also
enable further lockdown of the WindowServer process since it should no
longer need to pledge proc and exec. :^)
Note that this program is not finished yet.
Work towards #1231.
