- corrected sorting 0.2.10 > 0.2.2

Enable iterative initialization for target='opencl'

See merge request pycodegen/lbmpy!24

CI: Replace minimal-ubuntu job with ubuntu

Closes pystencils#19

See merge request !22

- works on newer VS compiler locally
- comment this test out until CI system is properly updated

- test_serial_scenarios already tested if waLBerla is available by catching ImportErrors
- importorskip from pytest throws another exception, which is not part of the public API
-> catching all exceptions - which is not really elegant but works

- also for default MRT methods its better to use symbolic RR's instead of inserting numeric values for them
- but then the simplification strategy developed for SRT/TRT has to be disabled
- this commit introduces two new options:
     - simplification='auto' or a custom SimplificationStrategy
     - 'keep_rrs_symbolic'=True, by default now RRs are left symbolic

Execute LBM scenario with OpenCL

See merge request !13

Add custom timeloop_creation_function for LatticeBoltzmannStep

See merge request !20

Skip some tests if waLBerla is not installed

See merge request pycodegen/lbmpy!18

update of the kernel equations for the phase field model

See merge request !19

minor documentation fix for Shan-Chen

See merge request !21

are much faster in certain setups

With this update all derivatives are derived automatically with the functionality of pystencils.
Furthermore more testcases are provided.

- more time steps to get to stable solution

Use Gram-Schmidt for create_mrt_orthogonal

Closes #5

See merge request !17

- "mrt" now takes relaxation rates [shear, bulk, 3rd order, 4th order..]
- deprecated "mrt3": use orthogonalized mrt now
- fixed wrong test