Add a 'force override world_units_per_luxel' setting

[mikota]

Being able to add world_units_per_luxel key to func_groups/bmodels/etc is a very useful feature. It would also be nice to have a compiler flag which overrides these world_units_per_luxel keyvalues with whatever is passed as a command line option.

This would be useful because once you have a setup of a bunch of entities with world_units_per_luxel keyvalues, you're kind of stuck with it, since undo-ing each one manually in TB would take a bunch of time. This is a problem if these entities have low world_units_per_luxel values, for example if you want to compile most of the map with 16qu per luxel, but you mark a bunch of faces with 2qu or 4u per luxel for some specific shadow effect. In this situation, even a fast compile with -world_units_per_luxel 32 or something passed via commandline will take a long time because those specific entities will still be compiled with 2qu per luxel or whatever.

And so it would be nice if there was a commandline flag or something of that sorts which would make the compiler ignore the world_units_per_luxel bmodel keys and instead use the world_units_per_luxel passed via cmdline for all faces :>

[SirYodaJedi]

Perhaps something like -min_world_units_per_luxel (or something less mouthful) to clamp the minimum luxel size? This would be analogous to -minsamplesize in Q3Map2. Could also make an equivalent max size clamp, but that seems less useful than the minimum clamp.