Rename and deprecate Observations and ObservationsClass

[bsipocz]

These classes are way to generic, ideally the class name should keep some reference for the module they are coming from.
It currently affects 2 modules, mast and gemini.

[tinuademargaret]

My proposed name for the classes would be ObservationClass e.g MastObservationClass. That way there would be a reference to the modules they are coming from. If this is okay I would like to go ahead and implement it.

[bsipocz]

@ceb8 has to comment on what would be the preference, otherwise 👍 for the idea to pick up this issue.

[tinuademargaret]

Thanks @bsipocz. @ceb8 what do you think?

[ceb8]

I thinks that sounds reasonable. And then you would also turn Observations into MastObservations.

[tinuademargaret]

Great. Thanks @ceb8