Change the sum of log(p) & log|det J| to average of them, to solve the balancing problem

[Zhangyanbo]

When we need to add other loss components, the log(p) and log|det(J)| have to be averaged to make it easy to balance. This issue also make the https://github.com/ELIFE-ASU/Macro be hard to handle.

[Zhangyanbo]

Seems don't need this. And this feature may cause some unexpected behavior.