add setWindowFlags(Qt::Window) to improve window management

* improves window handling a lot
	(on Linux GNOME 3 at least: quickly resizing windows left/right, not forced in foreground anymore etc.)
	setWindowFlags() inserted in all *window.cpp files except mainwindow
    * some whitespace at EOL trimmed

dbc/dbcloadsavewindow.cpp

@@ -7,6 +7,7 @@ DBCLoadSaveWindow::DBCLoadSaveWindow(const QVector<CANFrame> *frames, QWidget *p
     QDialog(parent),
     ui(new Ui::DBCLoadSaveWindow)
 {
+    setWindowFlags(Qt::Window);
 
     dbcHandler = DBCHandler::getReference();
     referenceFrames = frames;