Added FocusedObject property

[dotMorten]

Adds a property to GestureManager to address Issue #9

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[UWarbs]

@dotMorten
I think the focused object change code look like this instead. (switch the 'OnGazeLeave' and 'OnGazeEnter')

            if(oldHitObject != currentHitObject) //The currently hit object has changed
            {
                 if (oldHitObject != null)
                    oldHitObject.SendMessage("OnGazeLeave");
                 if (currentHitObject != null)
                    currentHitObject.SendMessage("OnGazeEnter");
            }

[dotMorten]

@UWarbs I think you commented in the wrong PR(but I fixed it - thanks - dumb last minute clean up!). Btw. in the PR you can add comments directly to a specific line of code by clicking the + next to the line. Makes it easier to review and follow up.