OpenFOAM sources

[ahashibon]

For each source and header file it should be clear what changes SimPhoNy required and why. These should be documented for easy access, e.g., in the Readme and the comments in the respective files.

In addition, for each additional file that does not have an obvious meaning from the name or location, please add proper short documentation (e.g., for file_1, file_2, etc).