Tab support

Via Twitter (https://twitter.com/andreasjk/status/289311694365278208): "Any chance we will get tab support in a future version? It gets quite messy with multiple open repos in different windows."

Difficult because the toolbar is context-dependent, but I can see its usefulness having everything self-contained in one repo window. We also should remember people have multiple repo-windows open at once on different desktops and switch between them, so there's a number of obstacles that would need to be discussed on this one. The following would need to be addressed:

1) Tabs would need to be above the toolbar, because the toolbar is context-dependent. This in itself would mean a few problems (tabs being at the very top of the screen so difficult to see perhaps)
2) The ability to have separate windows rather than tabs because people have multiple windows open at once on different desktops. There would need to be an option to switch them on or off, or the user should be able to pull windows apart (like browsers allow you to do "Open in New Window" or "Open in New Tab")