macro-related naming and option

[paciorek]

@kenkellner @perrydv
We agreed to change:

• enableModelMacros -> enableMacros
• model_macro_builder -> buildModelMacro

Given we are omitting "Model" from enableModelMacros, perhaps we should go with buildMacro?

Also I have a note to myself for version 1.3.0 to "turn model macros on with nimbleOption".
But I think we already have this via the enableModelMacros option. Do either of you remember if there were something more here?

[kenkellner]

I like buildMacro.

I don't remember specifically, but maybe the note was to turn on enableModelMacros by default at some point? Right now I believe the option is off by default.