Fix bug in communicator pybinds

See merge request irmb/VirtualFluids_dev!252

Fix bug in pvtu file

Closes #116

See merge request irmb/VirtualFluids_dev!250

The data type in the .pvtu has to be same as in the .vtu file --> Float64

Update regression test with new reference data accordingly to https://git.rz.tu-bs.de/irmb/VirtualFluids_dev/-/merge_requests/209

Fix typo in numerical tests

See merge request irmb/VirtualFluids_dev!247

Unified Refinement (CF and FC) for gpu and cpu.

Closes #60

See merge request irmb/VirtualFluids_dev!209