Pointer Events pen with tilt, pressure and hover support tracker HD

Expanded the basic WebGL-powered demo http://patrickhlauke.github.io/touch/pen-tracker/ to show how tilt and pressure information (in this case, using the Wacom Intuos Pro) can be processed using Pointer Events. In addition (by checking when pointermove events are fired, but pressure is zero) the demo also shows when a pen/stylus is "hovering" over the digitizer - but note how tilt information becomes unreliable (for the Wacom anyway) when the stylus is too far away. Demo requires IE11 or Microsoft Edge and an advanced stylus/pen (for instance, the Surface Pen does not support tilt, though it does support pressure).