Spin-polarized Hamiltonians

[zerothi]

The spin-polarized Hamiltonians should be possible using sisl, however, there are mistakes.

Currently this is easy to bypass as one simply creates two Hamiltonians (spin-polarizations are independent)

[zerothi]

I have tried a simple work around by checking the def_dim variable, however this has some problems.
I think the only reasonable way is to split the sparse matrix into two components, H and S. Then we may align the patterns.
It has some cost as each sparse pattern will have to run the extend function, but maybe this is OK?
Tests of speed may be needed...

[zerothi]

This is already fixed, however it will be changed subsequently.