Initial implementation of multi-contingency app

[PhilipFackler]

Description

Refactored pdsim code as ContingencyStudy class and reused in initial implementation of concurrent contingency app.

Closes #392

Proposed changes

For the work-in-progress I implemented three different versions of the simulation for easy timing comparison.

• serial
• async (using std::async)
• openmp

The easiest interesting case to try locally is "new england" (I have 22 cores in my laptop).

Checklist

• All tests pass.
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows GridKit™ style guidelines.
• There are unit tests for the new code.
• The new code is documented.
• The feature branch is rebased with respect to the target branch.
• I have updated CHANGELOG.md to reflect the changes in this PR. If this is a minor PR that is part of a larger fix already included in the file, state so.

[lukelowry]

'ContingencyStudy' -> 'CTGStudy'

CTG is common short hand and way easier to type! One option.

[PhilipFackler]

yes, I need feedback on naming things

[pelesh]

A few comments:

• Great to have multiple execution options to compare performance!
• I suggest restoring PDSim as it was. It is a different app and should not be modified in this PR.
• I would contain implementation of ContingencyStudy to a single file or a source and a header file.
• We have development of application utilities in our roadmap, but this is beyond the scope of this PR.

[nkoukpaizan]

A couple of comments on this below. We'll also need to update the applications README when this is ready, to minimize users' confusion.

[lukelowry]

Very excited for this! I think once we have this merged we should address the events-as-components modeling so we don't need to store a BusFault for each bus in the case.

Also, if possible, I'd like the *.study.json to have a "ida_stats" field for a file output string that would if passed calls the IDA api and writes out the IDA statistics (verbose extended version). I would use that ASAP with this + PDSIM

[pelesh]

The new code needs to be better commented. The purpose of classes, structures and standalone functions implemented here needs to be better explained.

It is unclear what is the purpose of CTGStudy::run() function. This could be implemented within standalone function runStudy. I would suggest removing CTGStudy class altogether and moving utility functions for I/O processing to ContingencyUtilities.*pp file(s).

[nkoukpaizan]

Almost there I well. I'm able to follow what's in ContigencyAnalysis.cpp, though more documentation (runStudy, runStudyAsync, etc.) is always welcome.

I would add an example that uses the ContingencyAnalysis executable that shows how this works and runs along with the other tests/examples.