Include external Hamiltonians as submodule
We can add git.physik.uni-wuerzburg.de/ALF/hamiltonians.git as git submodule, so (combined with #286) it's very convenient to use non-standard Hamiltonians
We can add git.physik.uni-wuerzburg.de/ALF/hamiltonians.git as git submodule, so (combined with #286) it's very convenient to use non-standard Hamiltonians