Create `develop-WaterQuality` for work on non-hydrolic modules

[aufdenkampe]

@rheaphy, it seems that we might need to park all the in-development model modules from commit https://github.com/LimnoTech/HSPsquared/commit/989a096a9b7b438356324fce8353db0eff3c2669 into a feature branch, so that we use the develop branch to first work on our other priorities to merge into master when complete.

So this PR is part of creating that structure, so that we can use a Feature Branch workflow similar to:

I created this develop-WaterQuality from @rheaphy's Development branch, and this PR merges in all the commits that @rheaphy since made to master.

I'm thinking that we might use the develop branch to work on these first set of tasks in our Collaborative Work Plan:

• [ ] Expand testing system
• [ ] Update demos/tutorial notebooks to py3
• [ ] Issue first py3 release?

Meanwhile, we might use this develop-WaterQuality branch to work on these development objectives, perhaps even in parallel.

• [x] Share water quality Python code chunks from Fortran
• [ ] Develop a WQ module process
• [ ] Start working on WQ modules

We'll continue to merge into all updates from develop or master into this develop-WaterQuality.

cc: @PaulDudaRESPEC, @steveskrip, @ptomasula