Implement mouse handler in piechart

[Tanguylo]

• I'm submitting a ...

  • feature request

• What is the current behavior?
  The mouse handling is very basic and produces sometimes an unexpected result.

• What is the expected behavior?
  Mouse behavior to be managed as in workflow builder (with a mouseHandler class).
  Expected features :

  • Change style of parts on mouse over
  • Change color of parts on mouse click