docs: List default constructor in doc strings
docs: List default constructor in doc strings

Add default constructor to class docs strings as:
Object(**properties)

https://bugzilla.gnome.org/show_bug.cgi?id=708060

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