Duplicate common base.jl and solution.jl

[rb004f]

GasModels.jl and PowerModels.jl has common code that should be duplicated here (and then removed from GasModels and PowerModels)

[rb004f]

@ccoffrin This should probably be a staged approach

1. Duplicate the code we think should be duplicated
2. Write tests for that code (I am thinking we just have a simple flow model as the "Example" that lives in this package for testing and demonstration purposes).
3. Register the package
4. Remove the code from GasModels and PowerModels, and add InfrastructureModels as a REQUIRE

What do you think?

[ccoffrin]

Agreed. This is the process I had in mind as well.

Writing meaningful tests can be tricky. In this package the test probably need to be a bit more rigorous to ensure the dependent packages don't break with updates are made.

[ccoffrin]

I am a little hesitant to bring in the solution extraction code, as is, as this is something I have wanted to engineer for some time (lanl-ansi/PowerModels.jl#77).

[rb004f]

Ok, then maybe the re-engineered solution extraction code should be implemented here, and GasModels and PowerModels will conform to the new one once it is ready.