Add prototypes to swellrt objects

[atd]

There is code in Pear2Pear that should go to the models, for example:

https://github.com/P2Pvalue/pear2pear/blob/master/src/js/controllers/projects.js#L42

It would be fantastic if we could assign a prototype to SwellRT objects. In this case, we could just use:

project.progressPercentage()