unite components' navigation and CRUD actions

[rinusser]

Currently each component needs to implement their own save/revert/etc button handlers and each component UI needs to set up their own buttons.

Move the CRUD/nav buttons outside the Gtk.Notebook widgets and hide them if the current component isn't a CRUDComponent or doesn't have navigation.

Maybe:

• map Component instances to notebook tabs (so e.g. Reload() can be called on a .CurrentComponent field/property
• split navigation capability from CRUD components: e.g. daily analysis details could still be browsed