Fauxton: fix burger

- Fix z-index issue for Firefox, the burger doesn't need an own
  width and high z-index

- Fix accidental horizontal scrollbar in resize-handler

COUCHDB-2234
Remove unused transitions

They don't work any more since some time
Do not show version on a collapsed view
Readd z-index, fix height & width of burger

I think the initial intention was that the burger should be
visible and the content scrolls under it
Disable the scrollbar in the sidebar

It looks ugly on Windows and Linux and it presses the icons to
the left on these systems
Respect the height of the logo in the bottom
Fix Scrollbar issues

Fix the horizontal scrollbar, as the border of the dashboard
was not included in the calculation.

Fix the vertical scrollbar for resolutions > 1500 px, where
the scrollbar sometimes was around 50px next to the end of
the window.