Update qeq module

[gust-07]

1.Matrix inversion method and projected gradient method were added to calculate the equilibrium charges，and step stride was added to control method 2.units of Chi and J parameters were unified. 3.qeq test case was also uptated.

The following files were modified: dmff/admp/qeq.py dmff/generators/qeq.py tests/data/qeq.xml tests/data/qeq2.xml tests/test_admp/test_qeq.py doc/user_guide/4.3ADMPQeqForce.md