Move PropertyDataValueTypeLookup out of SQLStore NS

Change-Id: I1e9f214a1635eb3a70b565293b8a406c0f5cbb5b
Added some docs and TODO

Change-Id: Iad0be8365331daa96b24501302a44e4783b7c349
Merge changes Iad0be836,I1e9f214a

* changes:
  Added some docs and TODO
  Move PropertyDataValueTypeLookup out of SQLStore NS