mint-arena: Add flares to video settings

Saw it in Open Arena, seems like a good idea.
mint-arena: Fix over draw in CG_DrawRect

It was noticeable in the corners when alpha was less than 1.
mint-arena: Add effects color 2 to player settings

Backported from Turtle Arena. Added caption for what they control.
mint-arena: Add handicap caption in menu like Open Arena

Added "of a " because I think it sounds better.