Various pre-rewrite model cleanup and clarification

Removes interpInMass from Girardi
Removes FeH from globalIso
Adds new Isochrone

Adds new Isochrone class with appropriate handling from Girardi.

Chab, DSED, and Yale will not compile without commenting all references to 'isochrone'
Changes comment formatting in Girardi
Removes binSearch and structures

Changes to Chab, Dsed, and Yale still not pushed
Adds UVIS filters
Changes error messages in GirardiMsModel
Removes references to structures from sim/scatterCluster
Modifies assertions in GirardiMsModel which don't (and shouldn't) hold in simCluster
Removes SDSS from list of acceptable filterSets when using the Girardi models
Removes references to the main sequence from FilterSet and FilterSetName
Adds 'Invalid' stellar models

Adds mechanism to describe invalid stellar models, specifically those which can not be loaded due to requesting an unavailable filterSet.

Currently, this makes formerly fatal errors into warnings. Further support from individual applications will be required to ensure no crashes.

Closes #52
Closes #26
Closes #57
Updates makeCMD to the current back-end. It is not operational.
Makes exception more descriptive in densities.cpp
Adds first-try Yale implementation
Complete makeCMD rewrite

Complete, no reuse rewrite of makeCMD
Makes deriveIsochrone a pure virtual method of MsRgbModel
Corrects Girardi assertions

interpAge can fall on a model age boundary
Stubs out generic MsRgbFunctions
Adds helium curves to MsRgbModel
Rewrites DeriveAgbTipMass for EEP-based models with (possibly) more than one Y value
Fixes extra section boundary bug