[CF-340/CF-345] Productize Preferences Service
  - Added default timestamp for created and updated as the in-memory db for tests need them
  - Added "Unit" as return for the POST method.
Merge remote-tracking branch 'ss/CF-345_json_schema' into CF-345_json_schema

Conflicts:
	src/test/scala/com/rackspace/prefs/model/InitDbTrait.scala
Merge pull request #2 from ChandraAddala/CF-345_json_schema

[CF-340/CF-345] Productize Preferences Service