Support for ORSO model language via `orsopy`

[alexhroom]

The orsopy package can read in the (relatively simple) .ort model description format into a dataclass into a dataclass. This dataclass contains enough information to define most of a RAT contrast:

• Layers with parameters
• Bulk in & out
• Layer model list
  and converting from the dataclass to RAT classes would be relatively simple.

One potential issue is that the ORSO dataclass takes arbitrary units - we may need to use a library like pint to convert to RAT's required units. It may also be quite difficult to implement this in the MATLAB as there is no orsopy equivalent for MATLAB!

[alexhroom]

Turns out this is a bit trickier than expected: I didn't realise the model description format linked above is just part of a larger experimental data file which doesn't necessarily have to include said model description!