Compatibility with Git

This fixes using redmine_jenkins with Git Plugin in Jenkins and git repository in Redmine.
There were 2 problems:
* the plugin couldn't find the revision number of a changeset (it's under "commitId" for git)
* plugin's JavaScript couldn't find the link to revision in issues (it's shown as short revision number for git)

BTW what was the reason for forking from https://bitbucket.org/nobiinu_and/redmine_hudson?