Start re-organizing the cylinder entry in equipment.c

Start re-organizing the cylinder entry in equipment.c

This leaves the actual editing code unconnected, so now you can only see
the cylinder information, not actually edit it.  However, with the big
re-organization I really do want to have this as a half-way point where
I have created the new cylinder tree-view.

I now need to connect the "add/edit" buttons to dialogs that then use
the editing widgets - so I've left that widget code around, because I'll
be able to reuse a lot of it.  Not all, but the cylinder type model code
in particular will be re-used pretty much as-is.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>