Implement dry_init and variable_eta_init Features in Multilayer Code

[mandli]

There's been a divergence in the force.

In reality there have been some features added to the single-layer main code and not to the multilayer code, which is not good. We need to bring the multilayer code up to feature parity. Some discussion on this was done in the #495 where @rjleveque did not think it would be too hard as long as things remained single-layered. This should be a priority before anything else gets added to the single-layer version of the code so that the divergence of features and code does not become too insurmountable.