Incorporated old changes to handling db recreation and locking; merged comments and new features; removed cell outputs
Incorporated old changes to handling db recreation and locking; merged comments and new features; removed cell outputs

Reviewed By: salexspb

Differential Revision: D4956379

fbshipit-source-id: 93e387a8873ebf95cdb1e7e249231e3ce285d518

pietern/caffe2,Yangqing/caffe2,sf-wind/caffe2,Yangqing/caffe2,bwasti/caffe2,pietern/caffe2,xzturn/caffe2,sf-wind/caffe2,davinwang/caffe2,bwasti/caffe2,davinwang/caffe2,xzturn/caffe2,xzturn/caffe2,pietern/caffe2,pietern/caffe2,bwasti/caffe2,davinwang/caffe2,bwasti/caffe2,sf-wind/caffe2,Yangqing/caffe2,bwasti/caffe2,Yangqing/caffe2,sf-wind/caffe2,davinwang/caffe2,pietern/caffe2,caffe2/caffe2,sf-wind/caffe2,xzturn/caffe2,xzturn/caffe2,Yangqing/caffe2,davinwang/caffe2