Scrawl-canvas v8 - DOM test 009

Stop and restart the main animation loop; add and remove event listener
Retrieve all artefacts at a given coordinate

Move mouse cursor over circles to make them opaque (when animation loop is active)
Click on the stack element to change direction of rotation (when stack listener is active)

Test purpose

Test manipulation of a set of stack entitys via their group
Test Group.getAllArtefactsAt functionality
Create and use a scrawl Color object to generate randomized color strings in a restricted range of colors

Move artefacts from one group object to another
Start, stop and restart the core animation loop
Dynamically add/remove event listeners to/from the stack

Touch test: should work as expected