Add main.py

[hlasimpk]

In SIMBAD/AMPLE we have main.py or something similar somewhere within the code base. Then the bin files are as follows:

ample
#!/bin/bash ccp4-python -m ample "$@"

ample.bat
@ccp4-python -m %CCP4%\lib\py2\ample\main.py %*

I think we want to do something similar here, as currently the /bin/mrparse file seems to act as the main.py file.