Possible to read nested json properties

The representation reader is currently not able to read nested properties.

> A resource in HAL is just a plain old JSON object with whatever properties you want [..] (http://goo.gl/mbgHU)

This is a small change to the property reader, which makes it use Jackson to parse the properties.

Things to be aware of:
* not implemented for xml
* all properties used to be strings... now jackson provides correct types

There is also a thread in the [Google group](http://goo.gl/lUfRx)