gtkmm: Auto-store editable TreeView cells

I just spent the weekend playing with template code to add easy auto-store editable cells functionality to Gtk::TreeView. I thought it would be simple but I kept hitting template madness and pulling back from the brink. It works now anyway.

I’ve given up on providing one simple is-this-change-ok? callback because there are just too many types in play, what with the CellRenderers not sharing enough common interfaces. But I still think that this could be done in GTK+ itself some day.

Cactus just finished making his sensible orbit-cpp-cactus branch good enough for bonobomm, so we can forget about the dodgy cpp branch. People should expect me to be annoying until this gets into ORBit2 releases.

I can’t find a UK or European online custom T-shirt company. I’d really like to send Cactus one of these.

I need to start looking for the next contract soon, and I’ll be more enthusiastic about that when gtkmm goes stable. At least the current job has convinced me that I should never waste my time on MFC coding ever again, no matter what they pay me. I knew that before but I guess I needed to be reminded.