ZEPPELIN-131 clean loaded job from controller when chaning the job
ZEPPELIN-131 add PENDING status for job
ZEPPELIN-131 make default job scheduler parallel
ZEPPELIN-131 make ZqlJobManager take care of PENDING status
ZEPPELIN-131 doc for job status
ZEPPELIN-131 prevent polling loop run more than 1 times
Merge pull request #78 from NFLabs/gui_bug

GUI is messed up when there're job running.