RK4 Simulation unaffected by change in Forced Biomass

[rklasky]

After changing ForcedBio with random noise in an RK4 simulation, no noticeable change in output biomass was observed.

[kaydin]

Looking for forced biomass issues in AB simulations as well. Seems to have issues in some cases but not others.

• In some cases, works as expected
• In others, zeroes out biomass
• How should it work for stanza groups?

[andybeet]

Duplicate issue #41