PullToRefreshRotateGizmo Class

Implementation of PullToRefreshGizmo that uses a rotating image to show the pull progress.

The image is rotated by the amount of distance traveled by the click/finger.

When enough pulling distance is covered (more exactly, the one between _StartingPoint and _EndingPoint) the gizmo enters the "ready to refresh" state,

the rotation amount applied is damped by _ExcessPullRotationDamping (i.e. a value of 1f won't apply any furter rotation,

while a value of 0f will apply the same amount of rotation per distance traveled by the click/finger as before the "ready to refresh" state).

When OnRefreshed(Boolean) is called with true, the gizmo will disappear; if it'll be called with false,

it'll start auto-rotating with a speed of _AutoRotationDegreesPerSec degrees per second, until IsShown is set to false.

This last use-case is very common for when the refresh event actually takes time (i.e. retrieving items from a server).