This commit contributes to the use of monitor-aware Points and
Rectangles for the translation between points and pixels coordinates in
the Display Coordinate System. Since the Display Coordinate System can
have different scales (zoom) in different monitors, it is designed to be
not continuous in the points coordinates. Hence when we manipulate the
coordinates of a Point or a Rectangle object, it might end up in a
region which is between two monitors in the point coordinate system,
which we consider a gap. So, we need the context of the monitor on which
those points and rectangles were created in the first place to evaluate
the scaling factor. If the context is not available or the coordinates
were updated to an irrelevant value, a fallback method tries to evaluate
the right monitor for the coordinates and evaluates the scaled value
with that.

Contributes to #62 and #127