Tests if there is an overlap between this image, and the 'otherImage' given. This Image will be tested at the x1/y1 location, whilst 'otherImage' location is held using x2/y2.
By default, the x and y values refer to the top-left corner of each Image. If you pass in 'true' for 'isCentred', then the locations are treated as being the centre of each Image.
The collision check is a cheap bounding box check, which makes this very similar to the 'isRectOverlap' function.