Fix errors in getElementRect and dropCheck

If element has no rect return null/undefined from getElementRect.

If getElementRect returns no rect, count as a false dropCheck.
Dissallow inertia while gesturing

Inertia for gestures is currently broken.
Merge branch 'master' into inertia
Add actions array to inertia options

inertact(element).inetia({actions: ['drag', 'resize']})
would enable inertia for drag and resize action
Add inertia to option default value test
Add docs for inertia actions option
Fix velocity of first move event of actions
Set event.detail = 'inertia' if inertia is active