Get rid of the OutputData struct

[EmilSoleymani]

The OutputData struct in the OutputFormat.jl module was originally meant to store an instance of InputData, which contains all the values it needed for calculations, and to store all the relevant output values. These output value fields were never added, and currently, the OutputData only contains an InputData instance. Therefore, this struct is redundant. Removing it will require the refactoring of many modules.

[smiths]

I agree that we should remove the redundant data structure. Thank you @EmilSoleymani for creating this issue.