CDAP-531: add inbuilt Exit, Quit and Help Commands
CDAP-531: Update help command description
CDAP-531: Update PR according to last comments
CDAP-531: Add unit tests
Merge pull request #13 from cybervisiontech/cdap-531

CDAP-531: CLI (common) - Need to have inbuilt Help and Exit commands
Fix checkstyle
Merge remote-tracking branch 'upstream/develop' into CDAP-537
CDAP-537: added unit test