sharing: Fix long "file sharing" explanatory label
sharing: Add per-network sharing

Using the new D-Bus service from gnome-settings-daemon.

https://bugzilla.gnome.org/show_bug.cgi?id=727580
shell: Add GtkListBox helpers

Add helpers for GtkListBox sizing, and setting separators.

https://bugzilla.gnome.org/show_bug.cgi?id=732106
color: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
common: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
datetime: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
display: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
network: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
notifications: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
online-accounts: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
power: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
privacy: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
region: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
sharing: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106
universal-access: Use new listbox helpers

https://bugzilla.gnome.org/show_bug.cgi?id=732106