[MP] More robust fix for #450.

There are a number of ways that NaNs can reach the engine, and this is
then processed in R_FogFactor to produce an invalid index. This commit
provides a more robust fix for any NaNs which may cause a segfault.
[SP] More robust fix for R_FogFactor crash.
[MP] Fix #423: spectator bug after special move
[MP] Allow callvote kick to kick connecting clients.
Clean up kickother and giveother commands.  Plus allow them to work even if the host command caller is not alive.

This commit fixes #408.
[MP] Removed unused function G_ClientNumberFromName.
Also callvote clientkick range checks on the sv_maxclients value instead of absolute max.
[MP] Fix up ClientForString in g_svcmds.c
[MP] Tweak ClientNumberFromString to not use trinary operator.
[MP] Lets try fixing that one again.
[MP] Skybox now uses GL_CLAMP_TO_EDGE
[SP] Skybox now uses GL_CLAMP_TO_EDGE
Revert "[SP] Skybox now uses GL_CLAMP_TO_EDGE"

This reverts commit 4a1f72c974753991de463e589e063c33a15577d3.
Revert "[MP] Skybox now uses GL_CLAMP_TO_EDGE"

This reverts commit 3bd8364d337f8bfdb830c70dea7d6418daa41bae.
[MP] Fix copy-paste-error reported by coverity scan.
[SP] Properly memset weaponData field with sizeof array.
[SP] Make SP's FS further in line with limits / features from MP.
[MP] UI_HasSetSaberOnly + UI_TrueJediEnabled tweaks.
[MP] Removal of some unused CM functions.
Use sqrtf instead of SquareRootFloat.
[SP] Removal of some unused CM functions.
Add Coverity Status to README.md
[SP] Fix a not really visible anim bug in CG_PlayerAnimEvents.