Tons of improvements

Hi Jul,
I found your node.js module some weeks ago, it's wonderfull.
To introduce me, I am a french full-stack developer (JS, PHP), working since around 10 years on lots of projects.
I known the Symfony admin generator, which creates administration screens for Symfony models.
Since I'm working with node, I looked for something similar, to manage all my "primary" collections.

OK, so I'm using your module, but I needed filters, sorting, and lots of things to add flexibility on how to display or save the fields on my collections.

You'll find all my addings. I know that it's lots of code in a time to check, but it could improve lots of stuffs in YAMA.

I added a bit documentation on admin.add & admin.init functions.

Feel free to use this code and if you've some questions, don't hesitate !

Regards