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.
dspaceCollections[i] could NPE. i.e. if your site only has like 5 collections, the limit is 100. So, 0,1,2,3,4,  5..99 would NPE. If we fix findAll(context, limit, offset) above, that would be a safer way...