restore click and hover effect

wanted behaviour: when clicking on the menu, the subnavigation appears. Hovering to another menu entry so opens the according sub navigation similar to apple's menu bar
fix an issue with border line

the submenu has a 2 pixel border, this should be only one pixel
fix issue with clipboard height

item collapsed if border box was active
fix for issue #3413
fix for issue #3316
restore tabs
correct fix for #3316
Merge pull request #3615 from FinalAngel/support/fe-fixes

Some frontend cleanup