[feature request] pinned tabs at top (across all windows)

[bjohas]

This builds on #3. Give that the tab switcher has an option to show tabs from all windows, then I would propose a further option whereby pinned tabs (from all windows) are listed first, before unpinned tabs.

Rationale:

I often have certain web apps open (e.g. gmail, gcal, etc) that I want to treat like stand-alone applications (as you can on chrome OS, and then use alt-1,2,3... to open / return to them). In the Chrome browser, I normally pin those. If those pinned tabs then appeared at the top of the switcher list (in the order in which the appear, rather than last used), one could very quickly switch back to them.