Adds converter task to haar cascade data from OpenCV

Adds build task that converts new OpenCV training data XML to tracking.js format. That would allow importing all training data available (https://github.com/Itseez/opencv/tree/master/data/haarcascades) to run on the web.

After OpenCV changed the old format to this new XML we need to figure out how this data is placed in order to convert it:

New format:
https://github.com/Itseez/opencv/blob/master/data/haarcascades/haarcascade_frontalface_alt2.xml#L55

tracking.js format:

``` js
[20,20,0.822689414024353,3,0,2,3,7,14,4...
```

Start by comparing the linked OpenCV haarcascade XML, especially the new format around line 55, with the tracking.js array format shown in the issue. Identify how the new training data maps to that format; done means a build task can convert the available OpenCV training data for web use.

Written by the indexing model from the issue text.