Cleanup and Refactoring of Plant Structures

[Myoldmopar]

Pull request overview

This cleans up a few things in the code:

• Eliminate a repeated allocation made within the iteration loop
• Initial cleanup of some plant utility functions
• Change the plant data structure to use scalars for splitter and mixer -- we only allow a max of one each anyway, this should make a tiny dent in the runtime by not having to do lookups in the arrays (which are always allocated to 1...)

[Myoldmopar]

Ahhh, another nice no-diff cleanup. Merging.