[API change] assign a MarbleModel to AbstractDataPluginModels upon their construction

* plugin models will benefit from knowing exactly which MarbleModel they'll have to use
* the MarbleModel can be accessed via AbstractDataPluginModel::marbleModel()
SVN_SILENT made messages (.desktop file)
fix toString* test cases on machines with non-english locale
export operator==( Marble::GeoDataLatLonBox const&, Marble::GeoDataLatLonBox const& )

* fixes linking of AbstractDataPluginModelTest with gcc

Thanks to idis for reporting!
don't leak the PopupItem
PopupItem created in constructor, no need to check for its existance
web view created in constructor, no need to check for its existance
preserve model
introduce MarbleView
introduce MarbleGLView
introcude GlLayerInterface
clear depth buffer between layer rendering
TextureLayer
PlacemarkLayer
introduce triangulation algorithm for polygons

* taken from http://www.crystalspace3d.org/svnroot/crystal/CS/trunk/{include/csgeom/triangulate.h, libs/csgeom/triangulate.cpp}.
GeometryLayer
introduce GeoGraphicsScene::GlTile and use glDrawElements
adapt PlacemarkLayout
use shaders
GLRenderer