Add model checking and standardization

[billdenney]

Try to make a function that checks as much of this as possible.

1. Are parameters consistently named?
2. Are parameter labels consistently defined?
3. Do all parameters have units?
4. Are all covariates defined with units?
5. Are the dosing units and measurement units defined?
6. Are any unit conversions accurately applied for conversions between dosing and measurement units?

[billdenney]

Add simulation-based test to confirm simulation values are similar to expected values from the model.