onSet and onAppend callbacks

[amaatouq]

In addition to the between games/rounds/stages callbacks, we might want to add additional callbacks that are invoked when an event within a stage happens.

This could include a general onSet(.) and onAppend(.) callbacks or more detailed ones such as onPlayerSet(.), onRoundSet(.), onStageSet(.) and instead of Set/Append maybe replacing it with onObjectChangein order to be invoked whenever object.set("key",value) or object.append("key",value) are invoked.

[npaton]

Added with 6791675.