318759b6

By: ValentinHirschi <valentin.hirschi@gmail.com>

expose diagram analysis and make Python generation interruptible

User request: Add a method to get the UV superficial degree of divergence on a FeynmanDiagram.

User request: Also add a denominator_expression() on FeynmanDiagram

User request: Connect Python signal checking. At the moment the diagram generation is not interruptable.