Create fallback source

[dylanratcliffe]

It would be possible to create a source that is completely generic. This would mean that we could scan the server for the available resource types, and for all the ones we don't have real sources for, create a generic one on the fly. This wouldn't have as many links but would give us a lot of coverage for relatively little work.

I think we should try this before we make a start on #18 and #17