Implement hints on Robot

[x00l]

• A hint will display a thought bubble on the robot which will provide animated cues on how to perform an interaction
• It will not contain any text
• It will have 2 animated icons: the tool to use for the interaction, and the item it interacts with
• The hint will be displayed when the robot enters the designated area of an interactive item
• The hint shouldn't display if the robot is just passing by, only if he "expresses interest" in the item, for instance by slowing down by a certain amount.

[x00l]

Checked in: 7d36f28