Improve Copay's documentation: an example

I'd like to start improving most of our classes by using JSDoc (documented here: http://usejsdoc.org/)

This is an example of the end result of adding this documentation: http://eordano.com/jsDocExample/Logger.html
Oh, I rebased to take out this commit. Damn, the build will fail.

Did you take a look at http://eordano.com/jsDocExample/Logger.html ? It was generated from this file :+1: