they can be changed while the simulation is running

This restructuring allows for easier separation of modules into
separate repositories later. Also, now pip install with repo url can be
used.

The setup.py files have also been updated to correctly reference each
other. Module versions are not extracted from git state

- removed warnings from generated code
- made generated code string deterministic, generating the same twice
  gives binary equally files now

- small (length < 5) arrays with shape and stride information had to be
  memcpy'd to the GPU before every kernel call
- instead of passing the information as arrays, the single elements are
  passed
- leads to more function arguments, but simplifies GPU kernel calls

-> changes in all backends required

- Equilibrium class did not do "+1" density shift correctly
- support for generating single precision models

- test run again
- notebooks not yet

- works for 2D models now as well
- moved lattice boltzmann code generation to lbmpy_walberla module