[indicator] Use propertiesChanged from dbus properties interface

This switches to using dbus properties interface instead of network managers built in as this got deprecated and removed in newer versions of network manager [0]

This fixes many issues with the indicator

[0] https://developer-old.gnome.org/NetworkManager/stable/gdbus-org.freedesktop.NetworkManager.html#gdbus-signal-org-freedesktop-NetworkManager.PropertiesChanged

Fixes: #79 (closed) Fixes: #89 (closed)