This enables including the modules in this repository to be easily
included in conda environment specifications or to be installed in
a virtual environment via `pip install .`, or by installing from
the Git repository.

In this version it enumerates as modules to be installed all .py
files starting with a capital letter. Scripts etc in all-lowercase
files are therefore not installed, but this could be added where
useful. Also, it is probably better then to create a proper package
structure.

This is being called by NeuralConfig.py in BlueSTARR,

Apparently NeuralConfig in BlueSTARR relies on this.

Brings the code in line with what the method names suggest. (Otherwise
dict[key] will already die with a KeyError if the key is not in the
dictionary.)

Also makes the formatted error strings work.