Start displaying comments and drafts.

Added drafts() call to CommentApi.

Added CommentBox for displaying comments.

Modified CodeMirrorDemo:
1. Implemented the algorithm and data structure that, given a line
number on one CM, return the corresponding line number on the other.
2. Added methods to display comments.

Modified some CSS styles for DiffTable.

Added wrapper for LineWidget in case we need it.

Change-Id: I9b9f6940ffa4eb1f87f79d5a655edd6beaab3b37
11 files changed