0.7.0 - Whiteboard sample and expanded hook/grabbable interaction

Whiteboard sample:

• Added a sample whiteboard gadget and used it to shake out a bunch of issues with Aardvark itself.
• This appears in the gadget menu with a blue quad (Still needs an icon model).
• Dip markers in the colored cylinders to change the color of the marker and move the marker on the board to paint
• Markers and paint buckets from one whiteboard will work on another.

Grabbable/Hook interfaces:

• Both grabbables and hooks now have an interface list that takes a name and a function for each interface.
• Interface name should be of the form @. This is the globally unique identifier of the protocol that two of these components will use to communicate with each other.
• When a grabbables comes within range of a hook, Aardvark selects the first interface name that appears on both lists and includes that information in the "highlight" notifications to the hook and the grabbable.
• AvGadget.instance().sendInterfaceEvent() now allows a hook or grabbable to send a message to its counterpart for a given interface. These messages are received by the callback function that was registered when the hook or grabbables was created. These messages must be objects, but other than that are opaque to Aardvark and are passed through unmodified. The data in these messages is intended to be specified by whoever generated the interface name and version.
• Added onTransformUpdated to hooks so that they can get hook-relative transforms for any grabbables that match their interfaces.

Aardvark-react:

• Added AvPrimitive component, which makes it easy to add a sphere, box, or cylinder of whatever color to your scene graph and put the origin of that geometry on whatever part of it makes sense in your instance. See the whiteboard sample for how it can be used. This is just a helper around an AvTransform and an AvModel that does a bit of math for you.
• Added model scale and color to the handle in AvStandardGrabbable

General:

• Significantly increased the descriptor limit so that avrenderer will run out less often.

Monitor:

• Added the persistent name to the node display so it's easier to tell what's what.
• Improved propVolume rendering to support boxes.

Server:

• Manifests files and the model directory are now readable cross-origin.