Provide nicer displays for GenericPowerModel

[yeesian]

They are currently not terminal-friendly for interactive usage.

[ccoffrin]

How would this be different than the print_summary function?

[yeesian]

print_summary is for the network data dictionary. I imagine they could be the same, but perhaps users might be interested in a more compact display, and see model specific information (e.g. number of variables/constraints/etc) based on the formulation of the GenericPowerModel too?

Currently

network_data = PowerModels.parse_file(case3file)

looks nice in the terminal (since it renders as a Julia Dict), but

pm = build_generic_model(network_data, ACPPowerModel, PowerModels.post_opf)

clobbers the terminal screen (when rendering pm.data).

[ccoffrin]

Good point. Something more summative would be preferable in that case.