Merge gnome-build into anjuta

[Sébastien Granjoux <seb sfo free fr>]

Hi,

Anjuta seems to be the only user of gnome-build so I have moved it into 
Anjuta. It avoids some duplicate code to handle plugins. And I hope it 
will make this code more visible as it needs quite some improvements.

Anjuta doesn't need gnome-build anymore, perhaps gnome-build could be 
removed from gnome 2.26.

Regards,

Sébastien