ModelMapping validations at construction

[VEZY]

Add more validations to ModelMapping and remember using fields to avoid recomputing things repeatedly. Check more things and make recommendations to the user. Done by adding ModelMappingInfo and info fields on ModelMapping with: validated, is_valid, is_multirate, scales, models_per_scale, processes_per_scale, declared_rates, vars_need_init, model_specs, and recommendations.

Also detecting multirate from mapping metadata, and removing the multirate=true from run! (not required by the user anymore). This information leaves in mapping.info.is_multirate.

Check that all variables mapped to another scale are computed at this other scale (either by a model, or passed as a Status, or computed by a model at another scale onto this scale).

Check which variables are never computed and needed in the Status (per scale if it is multiscale)

Richer ModelMapping printing.

Add more information about the difference between Integrate and Aggregate policies.

Hard dependencies are ignored when the child and the parent are at the same scale and same inferred/declared rate, i.e. no need to provide an InputBindings nor an OutputRouting even thought the models have similar outputs.