v0.19

• refactored rendeing pipeline
  • moved all random displays to madcad.rendering
  • moved some specific displays to submodules like madcad.kinematic.displays or madcad.displays
  • moderngl and Qt are now optional dependencies in madcad source code (not yet optional for pip though ...)
  • different Qt wrapper versions are supported: pyqt5, pyqt6, pyside6
  • improved API for onscreen and offscreen rendering
  • making room for future 2d rendering
  • we now have decent selection management in the scene, and selectable objects can be hovered
• Solidelements can now be accessed either as attributes or items
• fixes and naming improvements in madcad.gear