Add better warnings to energy differences between GOMC/NAMD

[bc118]

When the energy warning happens for energy differences between GOMC/NAMD, added a more description comment.

Example:

• The warning may be caused by use of dihedrals in NAMD and not in GOMC.
• The warning may be caused by fixed bonds and angles in the GOMC FF file.

Maybe also check the differences between the FF files used for NAMD and GOMC and see if the K constants and r_o and theta_o ... are the same between them.