add `*.pyc` (python byte code) to ignore list

`*.pyc` are produced if python based tools are used in `src/tools/bin`
make adjustments suggested by @ax3l
remove DIM3D-only precompiler flags for radiation plugin
change loop over all super cells to work with arbitrary dimensions
adjust global position to work in 2D
adjust output-file naming for `perGPU` in case of 2D
adjust how guardig cells are avoided
correct typos