General Simplification and Rearchitecture

[olynch]

Most things are rewritten

[olynch]

There is a still a lot to do on this branch before we can merge, i.e. features to reimplement

• [ ] Dialogues/help menu
• [ ] Forms
• [ ] Box sprite
• [ ] Petri and elements demos should work again
• [ ] Zoom/panning
• [ ] global CSS and marker handling