Adding CSS styling support for the tabbed properties in the properties
view. This includes styling of the TabbedPropertyTitle (title bar on
top) and styling of the TabbedPropertyList (the tabs on the left).

Change-Id: I0b2c1e174a7f1fdf55734298803df3c7ae97c5d8
Signed-off-by: Matthias Becker <ma.becker@sap.com>