application: mark two user-visible error strings for translation

Even if these strings are only displayed on the console, they're user
visible errors, so they should be marked as translations as the others.
This is more visible since they're composed by a part which is
translated, resulting in possibly half-translated strings, such as
reported in

https://bugzilla.gnome.org/show_bug.cgi?id=666006
Updated Indonesian translation
Updated Galician translations
Updated Polish translation
Add a spinner when computing the contents of folders

In the process fix a problem where we were cycling in the
callbacks from file "changed" and "updated_deep_count_in_progress".

https://bugzilla.gnome.org/show_bug.cgi?id=78789
Add an icon to the location entry and drop use of location bar

https://bugzilla.gnome.org/show_bug.cgi?id=683598
Only show the spinner if the deep count take longer than a second.

This avoids flashing it on and off when it isn't needed.

https://bugzilla.gnome.org/show_bug.cgi?id=78789
Don't offer to show selinux context in a column by default

This field is cryptic, far too wide for the view, already displayed
in the properties dialog, is available through other means, and is
an implementation detail that isn't settable by users.
Updated Spanish translation
Remove some unused code
Updated Portuguese translation
Updated POTFILES.in
Assamese translation updated
Remove obsolete app icons
Fix file leak

https://bugzilla.gnome.org/show_bug.cgi?id=683769
Fix string leak

https://bugzilla.gnome.org/show_bug.cgi?id=683769
Fix gfile leak

https://bugzilla.gnome.org/show_bug.cgi?id=683769
Fix leaks

https://bugzilla.gnome.org/show_bug.cgi?id=683769
update Punjabi Translation
Updated Slovenian translation