Move toolbar to the left and hide the menu bar by default

I've been using this layout for years and I'm happy with it. It's also
what has been shown in the screenshots since at least 2016, so let's
make it a default settings for the next release.

Everything is still accessible from the usual places, this does not
remove any functionality.

Change-Id: I213f64956d223dbcab7a3f9cfd2fe0e9c80dd5ad