zoomFactor defaults to 2
View2D zoom may animate pan
MouseWheelZoom interaction animates zoom
Debounce mousewheel zoom events
Change View2D function names

Also make the TouchZoom interaction no longer use a private View2D function.
Add a rotateNoConstraint View2D method
Make TouchRotate interaction use rotateNoConstraint
Add a snapToZero rotation constraint
Do not apply rotation constraint while rotating

This is on par to what the TouchRotate interaction does.
Make animating rotation possible
Animate rotation when releasing mouse or fingers
2DView refactoring

This refactoring makes animating zoom, as opposed to zoomByDelta, possible.
Animate zoom after pinch
Animate double click/tap zoom
View2D NoConstraint methods renamed
Merge pull request #261 from elemoine/zoomfactor

Change default zoom delta and animate mousewheel zoom