Add RequestItemHelpdeskStrategy, that can be enabled with Spring DI

Cleans up Sam's "hard coded" approach
DS-1945 RequestItem Helpdesk has options to contact requester, and author
DS-1945 Add request_message to requestitem DB table

Also, refactored requestitem to be a dspace-api "model", moved all DB logic
from XMLUI regarding this module to the dspace-api model.

Add the requestitem.request_message to display in the contact-author form,
so they can see what the original request message was.
DS-1945 Add license headers for requestitem changes
Restricted Item request form, add link to login page for members
For request-item move the you can login Button before the request item para
Merge pull request #1 from LongsightGroup/DS-1945-request-item

Request Embargoed Item improvements to helpdesk, contact, and login