Generic Binding Model update

[wlegrand91]

Added generic binding model implementation. Small changes to global_model.py to allow for some properties to be passed from the generic model, and new generic_binding_model.py file that implements the generic model. Also included are several new .ipynb notebooks and their corresponding model_spec.txt files that demonstrate a few examples. Will update with a readme shortly, and also I may have modified your example .ipynb and I can regenerate that over the weekend.

[wlegrand91]

OK So I added a README in the model_spec folder (contains the model.txt files) with some basic info.

Two things:
1: For now it will only solve for C in terms of the usual variables, which for our system seems to be the only one that works anyway.
I would like to make it more general, i.e. solve for all or maybe one specific, but I expect that this requires a specific formulation of mass balance equations.

2: I'm realizing that I developed this on a linkage that doesn't have the parent functionality. I don't think they have any involvement with eachother, and can check this once I update my linkage to that version.