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

shear previously ignored the diagonal moments and bulk didn't exist

- orthogonalize automatically if no moments from literature are provided
- must specify whether weighted or unweighted orthogonality is desired

Fluctuating MRT: requires weighted-orthogonal method

Closes #6

See merge request !15

Test for fluctuating LB, avg temperature and velocity distribution

Closes #4

See merge request !16

update phase-field allen cahn

See merge request !10

Fluctuating MRT: use the correct prefactors

See merge request !11

updated the functionality and the testcases of the phase-field model conservative allen cahn

- sparse UBB boundary kernel is not written correctly
- did work up to now by chance
-> switched to channel instead of LDC test

Shan-Chen tutorial

See merge request !8

implemented unconventional D3Q27 stencil by Abbas Fakhari

See merge request !7

implemented the phase_field model of Abas Fakhari

See merge request !6

- str(e) did work in previous pytest version
- but the correct usage is str(e.value)
- in newer pytest version the string for the e object is changed so
  the tests did not work any more

Remove obsolete fluctuatinglb.method_with_rescaled_equilibrium_values

See merge request !5

Fluctuating LB needs zero mean and unit variance random numbers

See merge request !4