Clean up layouts and use minisplitter everywhere

This patch replaces all uses of QSplitter with thin 1-pixel
splitters. I also fixed dock widget layouts in main windows
to do the same. Additionally I had to tweak the tabbars so
they look good in mini splitter layouts to avoid a double
left-border.

Reviewed-by: thorbjorn

src/libs/utils/fancymainwindow.cpp

@@ -33,7 +33,6 @@
 #include <QtGui/QDockWidget>
 #include <QtCore/QSettings>
 
-
 using namespace Utils;
 
 FancyMainWindow::FancyMainWindow(QWidget *parent)
@@ -41,6 +40,7 @@ FancyMainWindow::FancyMainWindow(QWidget *parent)
     m_locked(true),
     m_handleDockVisibilityChanges(true)
 {
+    setProperty("panelwidget", true);
 }
 
 QDockWidget *FancyMainWindow::addDockForWidget(QWidget *widget)