Performance Suggestion: Add "compiled" model support

[carldlaird]

This issue considers the addition of "compiled" models. That is, if we have a model that we know we want to re-solve repeatedly with small changes, can we generate a "compiled" version of some sort that allows us to do this much more rapidly.

I (@carldlaird) have prototyped a version for linear models that allows some changes.

[qtothec]

How do we want to define "small" changes? RHS updates? Activation/deactivation of constraints?

[jsiirola]

Archived on the master Performance Proposals Issue (#1430). Closing this performance proposal until active development has begun.