now saves r_shadow cvars that are available in the graphics options menu

now saves r_shadow cvars that are available in the graphics options menu
separated R_Shadow_NewWorldLight into R_Shadow_NewWorldLight to allocate light and R_Shadow_UpdateWorldLight to assign properties, so that lights can be updated in place rather than reallocating them (mainly saves on hassles with r_debuglight testing while editing lights, which were being renumbered by every edit)
R_Shadow_UpdateWorldLight now tolerates radius 0, color 0 0 0, and snaps angles to the 0-360 range

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@4495 d7cf8633-e32d-0410-b094-e92efae38249