The implementation of particle filtering tracker

This contribution aims to implement the tracker based on particle filtering within a generic tracking API that opencv has. The tracker still has to be worked on, but it has potential. This work is supported by Google within the Google Summer of Code 2013 initiative. Mentor: Vadim Pisarevsky.

Besides, the implementation, I've also added a few minor changes to the docs. First, upon agreement from the previous author, I've added some cosmetic fix to existing documentation. Second, I've changed the top README.md file, for it does not correctly display the sequence of steps needed to get things built.

It still remains to write the documentation, I will do so during the acceptance of pull request.