Investigate what would be required to move to Laplacians

[jlperla]

@ajozefiak It looks like the Laplacians repo is active again, and they have updated to the latest julia.

What would it take for us to upstream our changes (if they make sense) to that repo. The primary reason we wanted to do this was that there were too many dependencies in https://github.com/danspielman/Laplacians.jl/blob/master/Project.toml so we would want to try to get someat least Plots. But that could be a PR we constribute.

What were the other things you added or tweaked?

[ajozefiak]

The first part was removing a bunch of dependencies, as you have pointed out. The second was extending the new interface to allow the package to spit out a linear operator that we can use however we want as a preconditioner. The library originally did not allow us to extract the linear operator and instead had its own cg implementation.

[jlperla]

@ajozefiak Why don't you start by submitting a PR to that repo moving the dependencies that are not central to the main operations of the repo into the test = ["Test"] or whatever section. In particular, Plots.

Lets see how that goes. If he is willing to mere a high quality PR on that, then we can try to get our other stuff added which splits out the linear operator. No need to actually add in all of our own CG stuff, of course.