Stunner - Editors refactoring

Refactor of all editor classes around  the BPMN and DMN editors in order to, basically, make code easier to understand, to maintain and also to allow short term codebase decoupling for kogito (aka kogito fork)

This work implies:

• decouple kogito - BC classes/modules
• remove inheritance and refactor by decoupled composition of classes
• drop dead code
• drop kie-wb-common-stunner-kogito-api module (as part of a continuous work on refactoring all existing kogito code into a single place)