Rename Model source file and add docstring

Rename Model source file.

Add docstring to Model class.
Add derived class to model template

Update Model class with __init__() function.

Add new derived class with placeholder name to model template.

Add further placeholder names for documentation.
Initial commit of ini parser module

New ini parser module, to eventually store code to parse INI file
strings.

Add accompanying test script.

Update to parser __init__.py.