Freehand Update: drag to edit, passive functionality and bug fix for statistics (#392)

* Drag functionality for freehand tool

*  Fixed broken statistical calculation

* Tidied up some styling issues

* Fixed double call to endDrawing on disallowed drag attempt

* Refactored freehand mouseUpCallback

* Refactored freehand mouseDragCallback

* Refactored freehand mouseDragCallBack some more to reduce cognitive complexity

* Addressing code climate issues: reduced complexity of pointInFreehandROI

* Addressing code climate issues: reduced complexity of getSum

* fixed mouseMove re-enabling after mouseUp