AMT_EXTERN - Process a function from an external environment

Usage:

output = amt_extern(environment, directory, module, input, outstruct);

`environment`	String selecting the environment to be used. Currently must be `Python`.
`directory`	Diretory inside the environment. For example, `verhulst2018` for the model from Verhulst et al. (2018).
`module`	Module name to be called within the environment. For example, `run_cochlear_model.py` for the model from Verhulst et al. (2018).
`input`	Structure with the input parameters. All fields will be saved in the directory `out` within the `directory` in the file `input.mat`.
`outstruct`	Structure defining the output parameters. Each field's name defines the variable name to be read from a file named by the field with the ending `.np` in the `out` directory. Each field must contain a vector defining the size of the variable to be read. Up to three dimensions are handled.

`out`	Structure with the output defined by `outstruct`. The fields of `out` will have names as in `outstruct`. Each field will have size as given by the corresponding vector in `outstruct`.
`status`	Structure with the status and results, see `system`.