- Added UpdateDescriptor
- The unknown properties are ignored by default
- SOGroup will work with the field "members"
- Added some constructors for the POJO classes
- Added license/mantainer comments

Squashed commit of the following:

commit b75d355c8b071920dda0af5e2211ef5376b8d3e9
Author: Álvaro Villalba Navarro <alvaro.villalba@bsc.es>
Date:   Tue Feb 25 15:54:04 2014 +0100

    - Ignore unknown properties

commit 0f2ed736c6950f5531f461e33e10a92901075d86
Author: Álvaro Villalba Navarro <vn.alvaro@gmail.com>
Date:   Sun Feb 23 14:10:46 2014 +0100

    - SOGroup by now works with the members field
    - Subscriptions problem solved

commit 2972c259d33d6690f8ad1dc7bf22c1bd79287091
Author: Álvaro Villalba Navarro <vn.alvaro@gmail.com>
Date:   Sat Feb 22 17:05:16 2014 +0100

    - Added needed constructors for the POJO classes.
    - There seems to be a problem with the subscriptions

commit 49b79ccae29d5581c89ca62ea830a885d9135150
Author: Álvaro Villalba Navarro <alvaro.villalba@bsc.es>
Date:   Fri Feb 21 17:07:01 2014 +0100

    Forgot the headers

commit 48bef53bb698629bb6f613934853ff6af5db92ff
Author: Álvaro Villalba Navarro <alvaro.villalba@bsc.es>
Date:   Fri Feb 21 17:05:21 2014 +0100

    Add

commit 63925b781f124bff781ec1466a43afa48abab96b
Author: Álvaro Villalba Navarro <alvaro.villalba@bsc.es>
Date:   Tue Feb 18 16:20:10 2014 +0100

    Signature