Add --json option to review SSH command

Add --json option to review SSH command for posting code review,
message and inline comments via SSH.  Command reads the review
input from text file in JSON format, that corresponds to REST's
ReviewInput entity:

  $ cat review.json | ssh host gerrit review --json <SHA1>

Bug: Issue 602
Change-Id: I7e6f84b878b835cb7ea144cddd99702116d69b57
2 files changed