Use prefix for DatabasePaths

[Jammy2211]

A prefix variable is used in DirectoryPaths to store files in sub-directories:

    def save_json(self, name, object_dict: Union[dict, list], prefix : str = ""):
        """
        Save a dictionary as a json file in the jsons directory of the search.

        Parameters
        ----------
        name
            The name of the json file
        object_dict
            The dictionary to save
        prefix
            A prefix to add to the path which is the name of the folder the file is saved in.
        """
        with open_(self._path_for_json(name, prefix), "w+") as f:
            json.dump(object_dict, f, indent=4)

    def _path_for_json(self, name, prefix : str = "") -> Path:
        return self._files_path / prefix / f"{name}.json"

This means that the files folder has a sub-folder named the prefix and when loading from the aggregator we specify this folder:

data = aa.Array2D.from_primary_hdu(primary_hdu=fit.value(name="dataset.data"))

Can we implement the prefix in all DatabasePaths functions so it is stored in a sub folder in the .sqlite database? Is this a sensible thing to do? We want the API to mimick that of DirectoryPaths so the same function:

data = aa.Array2D.from_primary_hdu(primary_hdu=fit.value(name="dataset.data"))

Can be called irrespective of whether the database was run as a session or built via scrape.

[Jammy2211]

The following example script shows this issue:

https://github.com/Jammy2211/autofit_workspace_test/blob/main/scripts/database/session/general.py

It raises the exception:

Traceback (most recent call last):
  File "/mnt/c/Users/Jammy/Code/PyAuto/autofit_workspace_test/scripts/database/session/general.py", line 170, in <module>
    for data in agg.values("dataset.data"):
  File "/mnt/c/Users/Jammy/Code/PyAuto/PyAutoFit/autofit/database/aggregator/aggregator.py", line 120, in values
    value = fit[name]
  File "/mnt/c/Users/Jammy/Code/PyAuto/PyAutoFit/autofit/database/model/fit.py", line 310, in __getitem__
    return getattr(self, item)
AttributeError: 'Fit' object has no attribute 'dataset.data'