Add in Interaction.Crosshair.

Extends Interaction.Hover; draws a set of crosshairs and keeps the same contract as Interaction.Hover.
Pretty big conceptual API question.  Is the Crosshair concept an Interaction or a handler?

Feel free to weign in, but my understanding of interactions and handlers is thus:

Interactions are essentially a housing for handlers to play around in.  Interactions will feed the handler the data it receives and let the handler perform.  The reason I like this model is because it allows for handlers to be composed (Think of a house with multiple residents, essentially (Sure one resident may spoil the house for the other residents but at this this allows nice residents to work independently nicely))