Revert "Begrüßungsfenster"

This reverts commit 58d03711fbe2d6a7bfd1b4cb765d2349504e525b.
Project files specific to a single IDE (Visual Studio, Eclipse and so on)
should not be added to the repository.
Instead, they should be kept local to the developers machine.
[.gitignore] Exclude the Visual Studio C++-specific project files from version control.

The file extensions which are ignored by Git from now on are:
	.sln
	.vcxproj
	.vcxproj.filters
There is no guarantee that this list is complete.
If you discover that some other files should be excluded, too,
please add them to the .gitignore yourself.

Please add the additional ignores in one new category per IDE.
In this example, the new category has been named
"Additional ignores for Visual Studio".
New categories should also follow this scheme.