Fix some issues with community addons

[zer0k-z]

The PR makes it so the plugin is aware of community addons, but it doesn't seem to be fool proof:

• Still have random client crashes with de_dogtown every once in a while, but the stack trace points towards nvidia driver dll so it might be a me problem only.
• de_brewery always crashes the server with or without metamod+plugin.

[xen-000]

Oh shoot I didn't see this one, my bad