Commented Feature: Customized mouse gestures [9625]

Support customized mouse gestures
ZoomGesture
PanGesture
TrackerGesture

Also support showing tracker on mouseover without pressing any button.
Comments: I've implemented something for this: -Added gesture properties to PlotModel to allow mouse/keyboard modifier gestures to be set for all plot control manipulators. -Created GestureRequirements class (and related enums) for defining mouse/keyboard modifier gesture requirements. -Only implemented/tested in WPF Plot.cs, but GetManipulator method implemented in PlotModel to make it easy to implement in other projects Properties in PlotModel to set are PanGesture, ZoomRectangleGesture, ZoomResetGesture, ZoomInStepGesture, ZoomOutStepGesture, TrackerGesture. Patch is attached, hope you enjoy.