EC_GraphicsViewCanvas: clean up TODO for implementing keyboard input. Some code cleanup + mark down TODOs for cleaning up duplicate code while at it. Add line edit to the Canvas demo to test keyboard input; and so that appears the keyboard input doesn't work... Koste or Cvetan will continue the work on this.
Add new convenient Scene::Components function that returns list of all components of specific type in the scene. Clean up scene iteration in Scene.cpp
Demonstrate usage of newly added Scene::Components (produces much cleaner code).