SOPFLOW able to read contingencies in PSS/E format

[wperkins]

Merge request type

• [ x] New feature

Relates to

• [ x] SOPFLOW

This MR updates

• [ x] Header files
• [ x] Source code
• [ x] Manual
• [ x] Other

Summary

This PR makes SOPFLOW understand contingencies in PSS/E format. Like SCOPFLOW, the contingency file format is determined by the file extension: .con indicates PSSE, .cont is the ExaGO NATIVE (PTI) format.

Closes #107.

[wperkins]

@cameronrutherford, in this PR I've added a utility script. I did not see an appropriate place to put it, so made a new directory, scripts, and put it there. Is this a precedent that should be set?

[wperkins]

The Python script I've added converts ExaGO/PTI contingency format files to PSS/E format. This was used to generate input to PowerWorld from ExaGO cases. The script should be modified, or another script added, to go the other way. At this time, I don't have time to do that.

[cameronrutherford]

@abhyshr there are conflicts with the user manual that don't allow an auto-rebase, but with a re-review and perhaps some more documentation to explain the scripts added this is good to merge.