DS-2168: New REST api with CRUD operations.

JIRA url: https://jira.duraspace.org/browse/DS-2168

New REST api with CRUD operations over community, collections, items, bitstreams. More information and description about changes in REST api are in description at JIRA task.
We also tested the week before last parallel processing at REST API (hundreds of records at a time) with the ESB and we found a bug with a pool of connections. We did already fix our branch in the local repository. We check the code and at branch for DSpace community.