Separate examples, possibly tests, into their own repo

[RobertPincus]

@Chiil @menzel-gfdl As we expand the universe of gas optics treatments it would be nice to reuse as much of the example and testing codes as possible. A proposal: we separate the Fortran codes currently in examples/ and tests/ into their own repo and generalize them to work with any gas optics object. We write small modules for each specific gas optics implementation that define the specific gas optics type and initialize it with data. At compile time one links the general codes with the specific gas optics type.

Continuous integration would check out, build, and run the codes in the example-n-testing repo.

Comments? Planning to do this in January if it's ok.

[RobertPincus]

@vectorflux Curious if you have any thoughts on this too, esp. if it complicates CI that we're hosting.

[RobertPincus]

@skosukhin Also interested to know if you have an opinion on this question

[Chiil]

Happy to talk soon about organization of code and tests!

[RobertPincus]

After some discussion we've agreed to generalize the examples and tests to allow for different gas optics implementations, but not to remove the examples and tests from the main repo.