Implemented ValueSnakStore->storeSnakRow

Change-Id: I9e0b10048fcf3f62636cafa88d82d44fae74581e
Added tests for exception cases

Change-Id: Idecc6acc17ad9ecbba6f6333ec077a2149ba93e8
Rename QueryEngine Updater to Writer

Change-Id: I5151d77aa04240ccc091c33f07d004a9540ae30b