[Bf-taskforce25] RNA groups proposal

[Vekoon]

Hi, some time ago I had this idea which I already proposed to brecht in 
IRC and I decided to post it here too after reading campbell's e-mail 
about using structs for UI grouping. A couple of days ago I started 
implementing my idea.
Here's a demonstration of the current status: http://www.vimeo.com/2725856
In the video description you can find a link for more details. Also 
remember to download the source video if possible as vimeo's compression 
made it unreadable (it's only 15MB).
Also I know it looks scary all those lines for defining the groups but 
the process is really automatic as it is just copy/paste and changing 2 
strings (I exported all rna_object.c's groups in like less than 10 minutes).