Get rewrite up and running

[trulsf]

I had some time to look a bit closer at PiecewiseLinearOpt. Both to get better acquainted with the code and to see how easy it is to combine it with functionality of PiecewiseAffineApprox, I have had a look at the work Joey had started back in 2020 in the rewrite branch. As part of this I have done some minor updates and changes to have this up and running with the latest JuMP and using HiGHS for testing. I have also added an interface that matches what exists in the current version to run all tests.

I got most methods working (except MultipleChoice that will need some conversion routines from a vertex-representation to halfplane-representation and OptimalIndependentBranching that was just too slow).

@odow When you mention a complete rewrite in issue #54, did you consider using this branch as a starting point? It uses more dispatching and avoids the giant if-switch you mention. It also opens up for more flexibility in algorithms and number of variables (both input and output).

[odow]

Hi @trulsf, I've sent you an invite to become a maintainer. This should let you push to the jump-dev remote, and give you permission to merge PRs and close issues etc.

I had no plans for the rewrite other than it should happen 😄

[odow]

Since this is only v0.4.3, you have permission to make any changes you deem fit. We can do a series of smaller PRs if that's easier. There is no rush to tag v0.5.0

[odow]

Does the README need updating?