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
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
Don't verify symlinked target for I/O operations

Nautilus verifies the destination for free space, read-only ability
and such. This however doesn't work for symlink pointing to a directory.

Internally (in gio) we call statfs() but that actually stats the fs the
symlink is on, instead of the place symlink is pointing to. This appears
to be a limitation of POSIX statfs().

To work around this limitation, let's disable these extra checks when
destination is a folder and symlinked.

The bug manifestation are false error messages preventing to create a file
or directory when parent fs is read-only but contains a symlink to rw fs
which is the desired destination.

https://bugzilla.redhat.com/show_bug.cgi?id=844713
Update French translation
Updated Greek translation
Updated Marathi Translations
Quote the use of file type descriptions in error messages

So that we don't have things like:
"There is no application installed for backup file files."

https://bugzilla.gnome.org/show_bug.cgi?id=683752