Add option to not generate log-files

[sjoelund]

I now have 3 million files like /tmp/openmodelica.hudson.objid.0c3f41ef40b543f48a84395c1d393d9c.log because OMPython doesn't clean log-files after it is done. I believe we should have more options:

• Output log to file
• Output log in memory to the OMPython object (a stream or a string?)
• Skip outputting the log (to save memory)
• Output log to stdout