[Feature Request] Formatting

[junghans]

Formatting the ctp similarly to the other VOTCA modules would be nice, assuming you have clang-format-7.0.1 or newer installed, you can simply do:

cmake .. -DBUILD_CTP=ON -DFORCE_CTP_FORMAT=ON
make format

(I added the FORCE_CTP_FORMAT option recently as part of votca/votca#145 and it can be romoved after ctp is formatted.)