Fix spin-polarized hhg spectrum from multipoles.
For spin-polarized case the format of multipoles is
# Iter t Electronic charge(1) <x>(1) <y>(1) <z>(1) Electronic charge(2) <x>(2) <y>(2) <z>(2)
Fixed bug to match the above format.
Fixed bug in the calculation of spin-polarized hhg spectrum from multipoles.
- I have checked that my code follows the Octopus coding standards
- I have added tests for all the new features added in this request.