Provide API for remove obsolete shard objects

:Release Notes:
Provide API for remove obsolete shard objects;
changes on MojDb, MojDbShardEngine and test.

:Detailed Notes:
- Add MojDbShardEngine::removeShardObjects();
- add removeShardInfo(), removeShardRecords() to MojDbShardEngine;
- moved MojDb::addShardIdToMasterKind() to MojDbKindEngine;
- add MojDbKindEngine::removeShardIdsFromMasterKind;
- extended MojDbShardManagerTest with shard objects usage test;
- fixed bug in MojDb::put (was absent device id);
- add call purgeShardObjects() to MojDb::purge();
- add MojObject::delString()

:Testing Performed:
tested on build

:QA Notes:

:Issues Addressed:
[GF-38548] Provide API for remove obsolete shard objects

Open-webOS-DCO-1.0-Signed-off-by: Igor Kuksyuk <ikuksyuk@luxoft.com>

Change-Id: I6cb166234426a376b20d540b50638571933d1f69
Reviewed-on: https://g2g.palm.com/3358
Tested-by: Roger Stringer <roger.stringer@lge.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>