Bug report: TurbineInterface not covered in tests and examples

[misi9170]

In merging #888, the deploy-book action failed because I had forgotten to update some function calls in the TurbineInterface object on on floris/turbine_library/turbine_previewer.py. I've now patched this (I think) in #900

Looking into this more, the reason that I missed these is that TurbineInterface is not tested, and also not used in any of the examples.

I would suggest that we consider either:

1. Adding a test for the TurbineInterface or
2. Deprecating TurbineInterface and just going through the FlorisModel in the documentation (full deprecation would need to wait until a later major release)

[paulf81]

Based on this issue patched by #900 and the fact that it is only in documentation, it does seem reasonable to deprecate the functionality into FlorisModel, which will be more easily tracked

[misi9170]

An option is to have a convenience class that is a subclass of FlorisModel for the specific purpose of turbine visualization. I'll need to think a bit more about whether that's worthwhile.

[misi9170]

After some discussion, I have added deprecation warnings to the TurbineInterface and TurbineLibrary classes and have removed mention of them from the documentation in #996. I'm closing this as complete, and these classes will be removed or revamped in a future major version release.