Refactor sidebar/tabs visibility to use GtkAction

* Add some actions for them to Glade file and make existing widgets
use these actions.
* Remove use of ignore_callback and some preferences globals and use
action instead.
* Centralize code related to showing/hiding sidebar widgets.
* Leave `interface_prefs.sidebar_symbol_visible` and
`interface_prefs.sidebar_openfiles_visible` and keep them up-to-date
for backwards compatibility.
Add actions for message window tabs
Use action for toolbar visibility
Use action for statusbar visibility
Use actions for zoom in/out/off
Use actions for editor features
Move choose font colour scheme stuff to Glade