Add elementary Files to AppArmor profiles

[Danielle Foré]

Currently there some exceptions in the apparmor profiles for common file browsers, but this list does not include elementary Files:

```
  # 'Show Containing Folder' (LP: #1022962)
  /usr/bin/nautilus Cx -> sanitized_helper, # Gnome
  /usr/bin/pcmanfm Cx -> sanitized_helper, # LXDE
  /usr/bin/krusader Cx -> sanitized_helper, # KDE
  /usr/bin/thunar Cx -> sanitized_helper, # XFCE
```

We're currently patching this in:

```
  /usr/bin/io.elementary.files Cx -> sanitized_helper, # Pantheon
```

Would be great if it was included upstream! :)