I've added viscosity and wtf
maybe variable names are wrong
Print a message when maximal iteration is reached
coefficients seem to be right but still don't work
Revert "Store only two diagonal elements"

This reverts commit 079e3b4bb41f51c2879e2cd72798d28aaedd8472.
Comment out buggy printing of mu_tilda
Merge branch 'something-is-broken' into master