Fixes: Improved style sheet design

Details:
I'm now styling more controls and using a more consistent look
for things. To make the tabbar feel more natural I added a
web-like point cursor as well a sunken appearance.

src/plugins/coreplugin/core.qrc

@@ -59,5 +59,9 @@
         <file>images/welcomemode/rc_combined.png</file>
         <file>images/welcomemode/background_center_frame.png</file>
         <file>images/welcomemode/center_frame_header.png</file>
+        <file>images/welcomemode/btn_26_pressed.png</file>
+        <file>images/welcomemode/combobox_arrow.png</file>
+        <file>images/welcomemode/arrow-left.png</file>
+        <file>images/welcomemode/arrow-right.png</file>
     </qresource>
 </RCC>