Merge pull request #9 from jdhok/develop

Validate session id in query service resource and metastore resource
Add various modes in grill server - open, read_only, nodrop and etc
Updated with review comments
Merge pull request #10 from InMobi/server-mode

Add various modes in grill server - open, read_only, nodrop and etc
Add license header for new files
Fix query create doc - change 'op' to 'operation'