Incorrect documentation for some mouse hooks

[JordanMartinez]

Discovered in #656:

• onNewSelectionDrag: copied-and-pasted from onSelectionDrag. This should specify that the hook is run every time the user continues to drag the mouse after pressing on some unselected text but has not yet released the mouse
• onNewSelectionFinished: copied-and-pasted from onSelectionDrag. This should specify that the hook is run when the user releases the mouse after pressing the mouse on some unselected text and dragging the mouse to a new location

[JordanMartinez]

Closed by #681.