SCM 727 - maven-scm-provider-jgit

This pull request adds a new scm-provider for git.
The implementation is fully based on jgit and therefore does not need a native cgit installation anymore.

Some of the advantages arising by using this provider are:
* no native cgit installation required
* support of username/password (like for svn)
...

This PR is referenced in http://jira.codehaus.org/browse/SCM-727