Improvements to Type Hinting and Object Model

[g105b]

This PR fixes #89 - IDEs will not complain about the use of type hints or object inheritance any more.

I have used PHPStan set to level 5 checks to expose any ambiguous/incorrect uses of type hinting. My IDE is happy now!

[nreynis]

You should split this: it really is 3 PR in one:

• Adding static analysis tooling
• Exposing script
• Changing inheritance organization

All those are independent concerns, by tying them all together in one PR, you take the risk that none ever get fixed.