Resource discovery and share requesting

[mickenordin]

I have crafted two pr:s that go together:

• RequestShare: Introduce the notion of a share request #194
• ResourceDiscovery: This patch adds a new resource discovery mechanism. #196

They will allow an operator to optionally advertise resources, by displaying metadata. They also provide a mechanism for a user to request access to such a resource, if it is not public.

Should we add these? What do you think?