(Dis)Allowed file(type)s

[brianman]

A nice feature would be to be able to Disallow filetypes as well as allowing.
This could in many cases make it easier for the individial admins.
Say you want to allow all filetypes, except psd, could then do it like this:
"ALL,!psd"

[Nibbler]

If you want to disallow a filetype you can simply delete it from the filetypes table.