Cleanup csds

The CSDS has grown a lot through the years and became more and more complex. In this merge request, I am simplifying greatly the API in order to cleanup the code.

Modifications:

• The module .c files are removed
• A single function is needed for the modules
• The logfile header is slightly modified and now includes which fields are used for which particles (along with the writing order).

Fixes #752 (closed).