Shear Tool Todo

• We should add Shear to the toolbar
• Click and drag to increase amount
• Shear should have a manipulator to shear in any direction, the orientation on which is controlled by the Orientation setting, just like the Transform manipulators. Dragging any of the handles shears in that direction:

• Just like the transform gizmos, the manipulator should be visible immediately, not only *after* the initial shear operation.
• Add Tool Setting to switch between horizontal and vertical shearing - this affects the view-oriented shearing that happens when you just drag anywhere in the 3D View.

• Shear transformation currently only uses vertical or horizontal mouse motion, it should follow the axis when using the gizmo.