Move remapShader command from missionpack ui to cgame

Don't allow using remapShader command if sv_pure is 1.
Improve remapShader command arg handling and add usage.
Don't register g_redTeam in missionpack ui, done by cgame code

Same for g_blueTeam.
Don't let client change systeminfo cvars, fixup vm/user created flags

User and cgame cannot change CVAR_SYSTEMINFO if connected to a server.
trap_Cvar_Set now creates cvar with CVAR_VM_CREATED flag.
Stop calling Cvar_Set2 all over the place, it's hard to add more arguments. Plus hard to remember what the qboolean means.
Put all code for setting cvar from network server into a single function.
Say server, game, or cgame; not "restricted source" tried to change protected cvar.
Various other things.
Remove Cvar_SetLatched