Python bindings and Gtk3

[Mike Alexander]

You may already know this, but the Python bindings done’t work in the current master branch (they still use Gtk2).  I made a brief attempt to fix this, but I don’t know either Python or Gtk3 well enough.  

I also noticed a cosmetic issue that you may not be aware of because I use a non-default window configuration.  I keep the tabs arranged along the right hand side of the  window.  In the Gtk3 version these tabs are about twice as high as previously.  This means that my tabs don’t fit along the side of the window without scrolling.  Before they took up about 2/3 of the window height.  This is obviously not a fatal problem, but it is annoying.

In general, I’m impressed by how well this works given the magnitude of the change.  It’s going to be a big improvement.

      Mike