Run the transform function of pyramidsegment in place, reusing the image
data as both source and destination in cvPyrSegmentation. This avoids
copying the image back and forth and the extra memory.
Update pyramidsegment to inherit from GstOpencvVideoFilter instead of from
GstElement. This means less code and more uniformity with other OpenCV
elements.
The opencv element includes were full of duplicates and uneeded headers.
For example a few elements that stopped using gstcvopencvutils still
included that header file.