tests: Add tests for get/set_property()
tests: Add tests for get/set_property()

Re-use the new CPropertiesTestBase class for testing get/set_property()
methods.

https://bugzilla.gnome.org/show_bug.cgi?id=726999

pexip/pygobject,sfeltman/pygobject,GNOME/pygobject,sfeltman/pygobject,pexip/pygobject,sfeltman/pygobject,pexip/pygobject,GNOME/pygobject,GNOME/pygobject