Python components of DFTB+

The PEP 8 guidelines are the basis of the python style used in the code.

Pylint files are suplied (utils/srccheck/pylint/) for code checking. In many cases, python unit tests are also implemented (see test/tools/dptools/ for examples).

For example to test the straingen script for Python3 compliance, from the top of the repository type:

env PYTHONPATH=$PWD/tools/dptools/src pylint3 --rcfile \
utils/srccheck/pylint/pylintrc-3.ini tools/dptools/bin/straingen

while to test for correct performance:

make test_dptools