Set HildonNote margins during construction

Set HildonNote margins during construction

* hildon/hildon-note.c (+hildon_note_constructor),
(hildon_note_class_init), (+hildon_note_set_padding),
(hildon_note_rebuild): Install a constructor where to set the
padding properties in the note, so that it actually works fine.
Use hildon_note_set_padding() for this, and also to set it during
the note rebuild.