First steps for improving webarkit-cv

[kalwalt]

The project need a whole improvement but for now we focus on the OpenCV code side.
We import opencv in the Worker.ts file and there we organize most of the steps for the tracking process. I noted sometingh on this subject in the PR #7 and i will extends here:

• improve opencv loading mechanism see PR Feature improving opencv code #9
• We need to display correctly the found pattern, a sort of draw debug function to dispaly a rect around it, and a point in the middle, or at least a three axis 'arrow' and displaying the keypoints.
• Improve the detection and tracking phase in the worker.
• Docker image to build the whole project.

I think we can open specific PR's for every points of this list, to avoid big updates.