[#73354298]: add levels 14-17, fix bug, expose isCmdCurrentInQueue and goal.successState

Adding 4 new levels that are called for in the 2-3 and 4-5 scripts. They are slightly different from existing levels and described in this document: https://docs.google.com/a/code.org/document/d/1WZOjOm9SF6TV9eyIZUhQwWrBj5w-6ZGT9yifE0itgFc/edit#heading=h.8uvqx7180mq

Added a new helper function Studio.isCmdCurrentInQueue() which can be useful in defining a success condition. It is used by level 14 to test to see if the "say" command is active and attached to an "whenSpriteClicked-0" event handler.

Added a new concept called level.goal.successState. It can be used by level.goal.successCondition() functions to store state. the successState associative array is cleared between "run" button presses by the studio app code.

Fixed a bug when initializing event handlers for levels that only have one sprite.
Should this be `{}`?