Added call_global_change_callbacks method to cvars.

Fixed ConVar.make_public to actually make the cvar public.

Added ConVar.remove_public to remove the cvar from being public.

Removed an unnecessary check in ConVar.__setattr__.

Added new cvars.public.PublicConVar class that can be used to automatically set a cvar to public when loading a plugin and removing it from being public on plugin unload.

Added new cvars.tags.sv_tags object to easily add/remove tags from the sv_tags variable.

Added __len__ method to all filters.iterator._IterObject classes.  New len(PlayerIter()) returns the length at the time of calling.