* When a behavior or condition block is dragged over a breed/condition block
  (not yet dropped), a panel is shown at the bottom of the breed/condition block which
  indicates where the dragged block can be dropped.

* If the dragged block is moved outside the breed/condition block (or over another block
  inside breed/condition block) the indicator panel goes away.

* Visual clues are supported for BreedBlock and ConditionBlock