Visualization Doc Needs a round of Updates

[dnwillia-work]

• The API Reference page still says a single comment about describing the modules at a high level. This should be removed.
• The getting started page should be made at least conceptually consistent with the Fluent one
• The landing page could be tidied up: It still refers to PyFluent and it's features. This page should talk about the visualization package.
• We should add more examples about how to create and plot all the different object types, eg: vector plots are missing. Also, it would be good to document the controls in more detail. For instance on the Mesh object page it's not really clear what show_edges, surfaces_list or surfaces_list.allowed_values are actually for. The descriptions simply restate the name of the member variable which is not useful.
• For the Surface objects, what kind of surfaces? Is it for just boundary condition surfaces?, interior zones?, constructed surfaces like cut planes? etc.. This is not clear from the documentation. Same kind of applies to the other Graphics objects.

[PipKat]

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