Add reference files for examples that are used as tests

[nkoukpaizan]

Several examples are currently used as tests (CMake add_test), but don't have reference solutions to verify correctness. They are essentially smoke tests ensuring that the examples runs. Listing the relevant cases for PhasorDynamics here. It would be good to add reference solutions, at least for the smaller cases, with the understanding that validation for larger cases is contingent on merging some models.

• TenGenClassical
• TenGenGenrou
• Hawaii
• NewEngland
• Illinois
• WECC
• Texas
• ACTIVSg10k

cc @lukelowry @abirchfield @pelesh @PhilipFackler

[lukelowry]

Good issue to track. I am waiting until the last 6 models are merged so we can do this in one batch and only once