Merge branch 'feature/remove-newton-typetag-dependency' into 'cleanup/next'

dumux/common/start/instationarynonlinear.hh

dumux/linear/amgbackend.hh

dumux/linear/solver.hh

dumux/nonlinear/newtonmethod.hh

test/porousmediumflow/1p/implicit/compressible/test_1p.cc

...mediumflow/1p/implicit/compressible/test_1p_stationary.cc

...orousmediumflow/2p/implicit/incompressible/test_2p_box.cc

...porousmediumflow/2p/implicit/incompressible/test_2p_cc.cc

test/porousmediumflow/2pnc/implicit/test_box2pnc.cc

test/porousmediumflow/2pnc/implicit/test_cc2pnc.cc

test/porousmediumflow/3p/implicit/test_box3p.cc

test/porousmediumflow/3p/implicit/test_box3pniconduction.cc

test/porousmediumflow/3p/implicit/test_box3pniconvection.cc

test/porousmediumflow/3p/implicit/test_cc3p.cc

test/porousmediumflow/3p/implicit/test_cc3pniconduction.cc

test/porousmediumflow/3p/implicit/test_cc3pniconvection.cc