Feature improving opencv code

[kalwalt]

First chapter of improvements for webatkit-cv see issue #8
In this PR we implement these features:

• better import for opencv
• opencv now is compiled with the MODULARIZE option
• new class WebARKitCoreCV -> this class is responsable for loading trackables, detecting and tracking of trackers. That is all the code that was in the Worker.ts now is here. The WebARKItCoreCV is instantiated in the Worker.

[kalwalt]

i removed the file in the build folder opencv_js.d.ts, it was like this:

declare module 'opencv_js' {
    export function cv(): any;
}

this fixed the warnings in the editor but mke failing the build because is not correct. An example will be from opencv-ts https://github.com/theothergrantdavidson/opencv-ts/blob/master/src/opencv.d.ts but it's not strictly necessary for now. We can add this feature later.