Documentation still refers to floris.simulation

[paulf81]

Documentation still refers to floris.simulation

Per #1104, some documentation refers to the old code structure, including floris.simulation instead of floris.core. Searching the code-base I can see this happening in docs and also in some within code docstrings. Making this issue to flag these whould be updated.

How to reproduce

Search code base for floris.simulation

[misi9170]

While we're on the topic of documentation, it would be good to also address the confusing definition of r in the Gauss velocity deficit model, as discussed in #1102 .

[misi9170]

Also, looking back through recent discussions that were basically caused by lack of documentation, I'll add #1065 to the list

[misi9170]

Also calculate_y_plane, #1123