Develop a request system

[rudolfbyker]

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

Minimum

• Display a request form below nodes of type rsc_library_request
• 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.