WIP: Add model and declFxn handling for "nodeFunctions"/calculate

[paciorek]

Do not merge. This is just for seeing code diffs.

This is a first step in bringing together PdV's nimbleModel work in nCompiler and my work in nimbleModel plus sidework not in a repo on getting "calculate" to work.

The various pieces are in place. Key open items are:

• working through what needs to happen with compileInfo and managing the predefined instr_nClass and modelBaseClass and declFxnBaseClass to work in compiled operation.
• setting up an nList of declFxns that can be called by indexing