Interact nodes

 *   Adding Nodes
     -  (If you don't use Windows(*)) Click (with the mouse) on either the "Audio" or "Numerical" items in the FilterList, and one will appear in the center of the screen.
 *  Selecting Nodes/Wires
     -  Hover a finger (red) cursor over the required node/wire, and then "click" at the screen (jab at the screen with your finger, basically). Selected Nodes are outlined in green, and selected wires become red.
 *  Moving Nodes
     -  Select a node and then use the pinch and pan motion like before, and only the selected node will move.
 *  Removing wires
     -  Select a wire once, and then again once it has turned red.
 *  Drawing Wires
     -  Hover your hand over the source node, such that your finger is approximately directly over the leap motion. After a while the cursor should disappear and be replaced by the end of the wire. Move the end near another node and release (by moving your hand forward or back by enough), and the wire should snap to the nearest node.

In this branch, I've also made some style changes: 
 *  Inports are now outlined in green when busy, but keep their original colour (so the type signature of the node is known always). As a result, Audio ports are now called blue instead of green to avoid clashing.
 *  Outports behave exactly like inports now (before they just had a generic busy style, now, they share the type colour of the output type, and are outlined green when busy like inports).
 *  Wires highlight in green when busy, white when unattached, and red when selected (and could be deleted).


(*) For some reason, FilterList doesn't work on Windows, and it's a massive PITA, since I don't have a windows machine, it would just take me too long to actually fix whatever problem it is, so I'm just gonna go ahead and ignore it for now, cos it works flawlessly on other platforms. If someone with a windows box wants to debug for me, that would be great, but it's not really a priority.