changed Cmd_AddCommand to only work for console commands, not client commands execute...

changed Cmd_AddCommand to only work for console commands, not client commands executed on the server, Cmd_AddCommand_WithClientCommand has been added to allow separate command functions for console commands and client commands, this got rid of a lot of cmd_source == src_command checks
this refactoring fixes a security vulnerability in the clcommand builtin provided by KRIMZON_SV_PARSECLIENTCOMMAND, which was able to execute many commands on the server console, and that put the burden on the QC code to validate command safety, which was not intended
in short: this fixes a remote console command execution vulnerability that affected a few games/mods

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@6685 d7cf8633-e32d-0410-b094-e92efae38249