Make levelshot command take 2 pictures like used in Team Arena

screenshot* levelshot now saves images at screen resolution to
levelshots/mapname.ext, and a resized image to mapname_small.ext.

The size to resize can be set by "screenshot* levelshot <w> <h>",
height defaults to width.
Add support for levelshots/*_small to q3_ui

Remove extention from levelshot/* in cgame.
Merge remote-tracking branch 'spearmint/master'

Conflicts:
	code/cgame/cg_info.c
	code/q3_ui/ui_servers2.c
	code/q3_ui/ui_splevel.c
	code/q3_ui/ui_startserver.c
	code/renderergl1/tr_init.c