gobject: Add install_properties()

Since we added g_object_notify_by_pspec(), an efficient way to install
and notify properties relies on storing the GParamSpec pointers inside
a static arrays, like we do for signal identifiers.

Instead of multiple calls to g_object_class_install_property(), we
should have a single function to take the static array of GParamSpecs
and iterate it.

https://bugzilla.gnome.org/show_bug.cgi?id=626919



Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>