Patching some small details

This is the second wave of fixes for the 2.0 release. I hope that now everything is finally up to my expectations.

Fixed

• Graphs do now also have a fancy styled scrollbar if they get too wide. (78803c1)
• The box-shadow hack to extend <hr> separators came with some graphical artifacts on hdpi screens. This is now fixed. (3510ade, af067fc)
• Tables are now scrollable. This fixes many problems with content getting too wide on small screens. (b07c1cb)
• The breadcrumb navigation has been optimized slightly, especially on small screens. (8109209, 527743a, 8e97a90)
• The color of the "generated by doxygen" hint has been fixed if GENERATE_TREEVIEW=NO (f1e4263)