overviewControls: Adjust heuristic for hiding workspace switcher

The workspace switcher should be expanded when workspaces are in use.
Our current implementation assumes that workspaces are used when there
are windows on at least two workspaces. However workspaces are already
used when moving from a non-empty workspace to an empty one (presumably
with the intention to launch something on that workspace), so tweak the
heuristic accordingly.

https://bugzilla.gnome.org/show_bug.cgi?id=662457
Add a 'Show Details' menuitem in the app picker

Add a menu item that shows the details of the application
in gnome-software.

https://bugzilla.gnome.org/show_bug.cgi?id=643043
Bump version to 3.13.1

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