Add mercurial repository support.

Unit tests are not coded for the moment, I would like to discuss if a tiny mercurial repo should be embedded in source tree or remotely on bitbucket or others.
cleaner:

```python
tup = (socket.gethostname(), time.strftime("%Y-%m-%d_%H-%M-%S"), user, msg)
completemsg = "EasyBuild-commit from %s (time: %s, user: %s) \n%s" % tup
```