added simple typed properties

[a4blue]

The Idea of this PR is to prepare and add typed properties in the classes generated by propel. Goal was to still maintain BC Compatibility

In the future strict return types would be great, but it would cause compatibility issues with many projects

[dereuromark]

Any update on this one?

[mringler]

@dereuromark I think this can be closed too. As said above, the proposed changes are dangerous, and there was no response from the author in six month.