GUI should detect cored.py version mismatch and imn version stamp

```
The GUI and cored.py should exchange version numbers and verify they are
matching. Furthermore, cored.py should detect the version number of the
imported core module and throw an exception when there is a mismatch.

Version and date information could be saved to the top of each imn file.

This can be problematic when installing from source, and Python modules end up
in /usr/local/lib/python2.7/dist-packages and the binary package is also
installed to /usr/lib/python2.7/dist-packages.

Exceptions occur in unexpected places only after starting a new session.
```

Original issue reported on code.google.com by `ahrenh...@gmail.com` on 10 Feb 2012 at 4:40