Develop a request system

This is being done in branch dev-request-system.

Minimum

[x] Display a request form below nodes of type rsc_library_request
[x] Keep track of requests
[ ] Allow admin to accept / reject / ignore requests
[ ] Add a hidden attachment field (using PRIVATE filesystem) to the rsc_library_request type.
[ ] Send emails (with attachment) when requests are accepted / rejected

I'll add more when I'm not tired and can think straight.

refstudycentre / rsc_library