New repo for extra materials

[joepal]

I've now added a (somewhat crude) repo for extra materials for assets. You can find it from the user contributed assets menu, or by going directly to http://www.makehumancommunity.org/materials.html

Ok, the solution is not optimal: it'd be better to get a list of extra materials when viewing an asset, rather than having to go to the materials view and then search for stuff fitting said asset. However, atm, I'm not sure how to achieve the former in drupal. When and if I do so, I'll add the feature. But I'm pretty certain that that won't require re-uploading anything, so with the current solution it's at least possible to start sharing stuff.