InfrastructureModels Conventions Maintenance

[ccoffrin]

• [x] update to PowerModels v0.14
• [x] drop Manifest.toml from git and add to .gitignore
• [x] add "ResultCount" check in build_solution, otherwise JuMP.value() can fail (see PowerModels fix, https://github.com/lanl-ansi/PowerModels.jl/commit/b80f4fec6a0cd00e55d32a903f66106a5f71d47c)
• [ ] remove JuMP.optimize!, and merge code into optimize_model!
• [ ] in optimize_model! make optimizer an optional kwarg (see, https://github.com/lanl-ansi/PowerModels.jl/commit/8a8c9c0062b9a4ca0e0cf2fff7ccd33bace00d54)
• [ ] update core function names, build_model -> instantiate_model; build_solution -> build_result
• [ ] update post_* functions to build_*
• [ ] follow problem naming convention post_(mn_)<prob name>(_<variant>)*