Add preventDefault and drag axis options

preventDefault
--------------

Returns or sets whether to prevent the browser's default behaviour in
response to pointer events. Can be set to

- true to always prevent
- false to never prevent
- 'auto' to allow interact.js to try to guess what would be best
- null to set to the default ('auto')

drag axis
---------

interact.drag({ axis: 'x' || 'y' || 'xy' })

If set to 'x' or 'y', then the drag event sequence will only happen if
the direction of the first movement of the drag is along the given axis.
Try to drag other element if axis fails on target
Merge branch 'drag-axis'

Add preventDefault and drag axis options