Changed the bounding-box struct point convention to (cx, cy, width, height, angle).
The GetFrame member function from Tracker class now uses the cv::RotatedRect object to represent the bounding-box and draw it on screen.
The JSON and Protobuf communication between the backend and frontend still uses the (x1,y1)(x2,y2) point convention, the backend performs the adequate transformations.
-Moved the methods that handles protobuf data from Tracker to KeyframeBBox
-Displacement and scale keyframes are now properties of KeyframeBBox
-Changed interface that updates the KeyframeBBox properties.
It's now possible to adjust the tracked bounding box from the preview window. Some work is needed to make it generic to the ObjectDetection effect and future effects
