New python modules for writing received data into a logfile.

AbstractFileWriter.py provides basic writing functionality.
SimpleFileWriter.py is derived from that class and will be the used
class in the final project. For now it does not implement own
methods. Thos will be added later on.

Furthermore the old data server file was moved DataServer.py and the
actual invocation of the server is now done in main.py.
Minor changes to concerning location of includes.

Moved some includes into the respective c-file where only local
inclusion is required.
Minor call fixes to newlt introduced modules...

...and the way they are called from main.py...!