Adding isInsideByLocation to AbstractShapeMarker

 * Addresses issue #49 Marker needs .isInsideByLocation()
   function

 * Improves clarity of existing isInside() method on the
   interface

 * Includes test class
Merge branch 'develop' of https://github.com/jonnyelliot/unfolding into jonnyelliot-develop
Added comments, and extended tests for AbstractShapeMarker.isInsideByLocation.