Put the tadpole_equations() function into the corresponding model
class to avoid multiple definitions in case several models are
linked together
add test case which checks that different model libraries can be
linked together properly.
add comment to show the user where his constraints are applied
MRSSM: do initial guess for vu, vd and specify the SUSY scale
for the low-energy models use a custom initial guesser which guesses
the gauge and Yukawa couplings (plus some user-defined parameters).
Use MaxRelDiff which protects us from Nans
Bugfix: Make sure we convert the model parameter indices, which
are given by the user in the model file, to C form
Add variant of the MSSM where we demand Yukawa coupling unification.