[visuald generator] When generating a combined VisualD project file, generates nicer <Folder>.
                    Each source file structurePath is now relative to its own package.
                    Note: all sub-packages are conflated to the same <Folder>, because it seems VisualD can't display folder names with a colon.
Merge pull request #110 from p0nce/master

Nicer <Folder> structure for combined VisualD project files.