"on every frame" action names are inconsistent

[brian-swan]

The board object has an action called add on every frame. Other objects have an action called on every frame. They essentially do the same thing: evaluate the objects state on every frame. From a teaching (or learning) point of view, this is confusing. Suggestion: Change the function on board to on every frame.

[mmoskal]

I have added an alias. We'll perform automatic renaming once this gets to "current", see #30