Add Two-Finger Panning and some other attributes

[edman007]

Hi,

I made some modifications to this, the major changes are:

• New Attribute "max-scale", allows you to limit the scaling
• Bumped the version of the dependency pointerTracker (we really do need canceled events)
• New attribute "no-default-pan", set to true or 1 to enable. When enabled one finger panning does not work initially allowing you to scroll on mobile with one finger
• New attribute "two-finger-pan", disables one finger panning entirely, only two finger panning works, again, allows scrolling on mobile

These new attributes don't affect panning with a mouse. And I think these panning modifications are important on mobile so you don't accidently get stuck on a and can't scroll past it...

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[edman007]

@googlebot I signed it!