Fixing NullPointerException thrown while cube select queries for a dimension table.
Adding method to release session with public UUID.
Adding acquire and release session calls for Query Operations.
Adding Time dimension column to the dimension table.
Merge pull request #1 from sreekanth-r/npe

Fixing NullPointerException thrown while cube select queries
Fix setting cancelled state
Fix test cancel query
Merge branch 'develop' of https://github.com/InMobi/grill into restart
Update restartability only for launched queries