Modernizr.touch changes, as per #548

Modernizr.touch changes, as per #548:

* `Modernizr.touch` -> `Modernizr.touchevent` (but `touch` still aliased)
* `Modernizr.pointerevents` (CSS pointer-events) -> `Modernizr.csspointerevents`
* Added test for [DOM PointerEvents](http://www.w3.org/Submission/pointer-events/) as `Modernizr.pointerevents`

*API-breaking change.*

I've done the PointerEvents test by checking for presence of the `pointerdown` event. [Microsoft's recommendation](http://blogs.msdn.com/b/ie/archive/2011/09/20/touch-input-for-ie10-and-metro-style-apps.aspx) is to use `window.navigator.pointerEnabled` (prefixed), but it isn't clear if `pointerEnabled` is intended to change dynamically as devices are connected/disconnected... anyone know? We agreed on #548 that Modernizr should focus on *static capability* to support pointer events, not dynamic state of whether or not an appropriate device is connected.

Review please!