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