Remove generated code from the index

Currently, some code that was generated (i.e., the model code) is also part of the history. Whenever the model changes, there is a huge potential that a lot of files will be changed in the process as well.

Solution: remove code that is generated from the current head revision. Coe is generated in the de.tu_bs.ccc.contracting.idl package and the de.tu_bs.ccc.contracting.mm package.