pull-request-event: modify column type new_value and old_value to clob
Rename SimpleComment to PullRequestComment
Add an info log for comment submit failure.
Improve Pull Request Comment

* Render code diff of pull request.
* Show outdated comments
Render code diff at server-side
Remove duplication from CodeComment and PullRequestComment.

1. Rename CodeComment to CommitComment
2. Create new class "CodeComment" and make it CommitComment's superclass.
3. Pull up lots of members from CommitComment to CodeComment.
4. Make PullRequestComment to extend CodeComment.
5. Remove many members of PullRequestComment duplicated with CodeComment.
Fix server-side diff rendering.

* Remove unnecssary codes.
* Fix some bugs.
PullRequestComment: Improve isOutdated()
Remove dependency of CommentApp.delete on the other controllers.
commit: Render diff at client-side for subversion.
PullRequest: Verify comments.
Improve code diff and line comments.
Fix FullDiff to work also for PullRequest comemnt.
Add more fields to PullRequestComment.toString.
Merge pull request #133 from npcode/yobi refs/heads/feature/improve-code-comment
Remove import of DiffMatchPatch to fix compile error.
Fix a constraint violation caused by 41.sql
Add missed column 'commitId' into PullRequestComment.
Verify pull request comments before show them.
Verify linenumber before show pullrequest comment.