Save view config when closing tab

This is a feature as well as a bug fix. Feature because now if you close a view and reopen it within a session, position will be restored for new views. Bug fix because we read the config when creating the view, which restores the config (if any) when kate was opened. This can lead to annoying things like in the last session I left a file at position{10:10} but after opening I moved to {20:20} and closed the document. Reopening the document takes me back to {10:10} instead of where I left it. For new views nothing gets saved at all so position is never restored.