#122 class/code to limit image sizes

[Lance_]

Please include in core the ability for admins to specify a
maximum global site image size width, and in the process
allow mod developper to specify a maximum image size
in their mods pages. (this size would have to be smaller
than the global size set.)

Too many sites are thrown off by too large images in
the different sections. (Forums being the main one)
Right now it isn't possible to have linked images limited
to sizes, uploaded images work fine in newbb2.

Thanks.