TextFileRepository/PersistenceContext needs reimplementation

[John Wilson]

It's currently not implemented using proper generics. We need a generic IRepository implementation that uses a factory or service locator to figure out the best implementation of storage for a given type.

It shouldn't be up to the object which needs its data persisted, to determine how it's persisted. So implementing a new repository should not look like

        private readonly IPersistenceContext<T> _persistenceContext;

        public TextFileRepository(Context context)
        {
            _context = context;
            _persistenceContext = new TextFilePersistenceContext<T>(_context); 
        }

instead it should look something like

        public TextFileRepository(Context context)
        {
            _context = context;
            _persistenceContext = new FooLocator<T>(_context); 
        }

where FooLocator looks at T and figures out what best to use, and returns something IPersistenceContext-y.

Normally we'd do this with an IoC container, but we don't have one yet.

[John Wilson]

TextFileRepository is now just IRepository. Still need to implement a proper persistence context service locator tho.

[John Wilson]

Going to keep the TextFilePersistenceContext for now. Might refactor everything later once I've got a better data-to-persistence mapping implementation.