LILY-2548 authz for remoterepo & lilyclient

Make RemoteRepository and LilyClient authorization aware:
 * RemoteRepository performs its direct hbase reads using the AuthEnabledHTable
 * LilyClient can take an optional AuthorizationContextProvider constructor argument. By default the DRAuthorizationContextProvider is used which takes it from the threadlocal var managed by AuthorizationContextHolder.

(all this stuff is only relevant when NGDATA's hbase authorization coprocessor is deployed within HBase)