Newton solver for `VariationalEntropyEvolve` and `VariationalMagFieldEvolve`
Solves the following issue(s):
Closes definitely #256 (closed) (the tests are now passing without any warning if all solvers are using Newton).
Core changes:
None
Model-specific changes:
Added newton solver for both VariationalEntropyEvolve
and VariationalMagFieldEvolve
. The default solver is Newton but Picard can still be use by passing 'non_linear_solver' = 'Picard'
in the parameters of the propagator.
Documentation changes:
None