Tabs above document file browser header in tab bar

Integrate visually file manager header in tab bar when tabs above document
option in on. If tabs above document are off then use default gradient L&F.

Bottom divider for file browser header view is not integrated in header for
easier control if it is shown or not.

See attached screenshot for provided look:
![zrzut ekranu 2014-09-28 23 17 22](https://cloud.githubusercontent.com/assets/103067/4435749/982a35bc-4755-11e4-90a8-1a4244a337a7.png)