Add top level exec script

[holzkohlengrill]

Feature Description

After the recent changes Emma can only be invoked via module calls (->like python -m Emma.emma --project doc/test_project --mapfiles doc/test_project/mapfiles --dir doc/test_project/results from the top level folder).

This is lengthy. Plus, an overall script for all modules would be convenient and will provide a better overview about the modules (a la git add or svn checkout, ...).

TODOs

• Add top level script named Emma.py
• Update documentation