Improve Marble's OSM vector rendering and printing support

by David Kolozsvari for KDE

The project's main focus will be on polishing various aspects of screen rendering and printing. This includes features like the OSM vector rendering, the printing support, the zoom with the mousewheel, some performance-tuning including patches and bug-fixes, and if possible improving the experimental OpenGL support too. Special focus will be on testing these improvements - especially the printing support -, to ensure compatibility on multiple platforms.