Make the time point of M and H more accurate in MacroscopicEvolveHM_2nd.cpp

[jackieyao0114]

1. To make the code cleaner, in the 2nd order algorithm in the static loop calculation, use Mfield_old instead of Mfield to make it clear these are old (static) quantities.
2. when H_Bias it time-varying, we really need and H_bias_old and H_bias_new in the static and dynamic loops, respectively.

[jackieyao0114]

Confirmed on May 2 that this is not finished. Need to resolve this ASAP.