RibbonView: RadRibbonButton has inconsistent pressed/focused state

The styling in the controls vary when the mouse is down.
- RadRibbonButton gets a black border.
- RadRibbonSplitButton gets an dark orange border (when clicking the dropdown button)
- RadRibbonDropDownButton gets a grey line at the top

On mouse over
- RadRibbonButton and RadRibbonDropDownButton have a dark orange border with a white inner border
- RadRibbonSplitButton (dropdown button) does not get the white inner border

Reason for declination: 
Currently there is no way to unify the pressed state of these buttons because there is no Pressed state of RadSplitButton (the toggle and button parts has their own press visualization that comes from the default style of the corresponding buttons).