cleanup solver
abstract solver
settable solver
move solver to engine
solver: remove *time
add euler solver
euler: require fixed time step
setsolver()
setsolver api
add euler test
implement cuda/temperatrue
temperature ready to use
temperature fixes, order of magnitude seems OK
temperature cleanup
temperature test
temperature cleanup
backup before quantity alpha*T/Bsat
temperature: do not crash on Ms = 0
ThermSeed()