Refactor mulliken charge analysis code.

[mohanchen]

…depth from 25 to 4

• Move cal_mag() template function to new cal_mag.h header
• Remove heavy includes (elecstate_lcao.h, dspin_lcao.h, density_matrix.h) from output_mulliken.h that were only needed by cal_mag()
• Replace output_dmk.h and output_sk.h includes with forward declarations in output_mulliken.h (class only holds pointers)
• Add output_dmk.h and output_sk.h includes to output_mulliken.cpp (implementation needs complete types)
• Update ctrl_scf_lcao.cpp to include cal_mag.h instead of output_mulliken.h

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