add additional UI buttons

[indig0fox]

1. hide map markers so only projectiles are shown
2. hide map marker names/captions (only applies to icons but globar var similar to existing implementation for units)
3. hide rect/ellipse markers so only units, icons, polylines are visible
4. hide units not part of the selected faction, to see one-way

i also plan to have firelines button control projectile visibility as well

goal for levels of visibility (not all variations listed of course): only one side's units one side's units plus firelines and projectiles all units plus firelines and projectiles all units plus icons and polylines (without captions) all units plus icons and polylines (with captions) all units plus icons and polylines (with captions) plus rect/ellipse 'zone' markers