Backporting DSpace REST API from DSpace 4.0 into our 1.8.x branch

Adding the new JERSEY based REST API from DSpace 4.0, into our 1.8.x branch of DSpace. 

Includes: 
DSpace REST : https://github.com/DSpace/DSpace/pull/323
Anja's fixes (except for statistics recording): https://github.com/DSpace/DSpace/pull/356