Enhance config file documentation

[rubenhorn]

In the couette.xml wiki…

• Add a more detailed description for input/output files (microscopic-filename, macroscopic-filename, microscopic-filename > filename/init-from-sequential-checkpoint, vtk-configuration > filename) or link to a separate wiki page explaining the file format
• Rename macroscopic-cell-configuration to coupling-cell-configuration
• Check for any other uses of “macroscopic cells” in place of “coupling cells”
• Fill out all TODOs for the tables