Improvements to GMM parameter constraints

Constraints classes for GMM implementations are not used in nshmp-haz as yet. Most need to be doublechecked against their publications and implementations. This creates some issues in as much as some GMMs over the years have been used outside their published ranges and so this needs to be noted in the javadocs.

Comment from @kmilner_usc.edu
I see the Constraints class lists which parameters are actually used, as well as their ranges...great, this is very helpful!! You might consider moving default values to here, as the constraint ranges don't always contain the Field.defaultValue (e.g., zTOR for deep models). My implementation also assumes that these constraints always return Range instances, do you expect to support other types of constraints in the future?

See also #42