Ocs-server/Gfx4/Filesystem utilities

GFX offers a static class as a file system helper. Small reference:

EFileSystem::get_file_extension(string $filename) -> returns string extension
EFileSystem::get_file_name(string $filename) -> returns string name
EFileSystem::rename_file(string $from, string $to) -> rename file
EFileSystem::move_uploaded_file_in($path,$newname) -> move uploaded file to $path and change name to $newname
EFileSystem::get_uploaded_file_name() -> returns original uploaded file name.