All mockups now use a representation for documents/places similar to
the one used for applications. Rename AppIcon to BaseIcon and move its
code together with WellGrid out of appDisplay to stress their general
usefulness.
https://bugzilla.gnome.org/show_bug.cgi?id=625887
Introduce the Universal Access status indicator as designed, modeled
after the similar UI provided by g-s-d. This indicator allows the user
to change rapidly the keyboard and mouse behaviour (sticky keys, slow
keys, bounce keys, mouse keys), as well as the enabled ATs (magnifier,
screen reader, screen keyboard) and the HighContrast Gtk theme.
https://bugzilla.gnome.org/show_bug.cgi?id=624916
This lets us share the recent-app-tracking, recent-file-tracking, and
icon-drawing code between the overlay and the sidebar, without the
sidebar having to poke into AppDisplayItem and DocDisplayItem's guts.