For i3 on the N900, which seems to be the only device using i3 at the
moment, I thought using Tabbed workspace layout as the default would be
best, since the screen is quite small, and having two split windows can
quickly make it impractical.
With this commit, all new windows will be created in tabbed
configuration. It is still possible to switch to stacking or standard
layout as needed, using the appropriate shortcut keys.
ec1016b385