Vectors

Add a new `vector` property off of the main Packet object which contains show, color, and direction properties.  This allows the client to render a vector at the packet `position` in the provided direction (and direction magnitude).

I also added a Direction schema which allows for direction to be specified as either a spherical or cartesian3 (which in turn required I add a Spherical schema since we only had a UnitSphertical.