change gen script to use ksh, remove namespace option, regen genfiles

rewrite scripts/gen-gdbus-interfaces.sh to use ksh (#!/bin/sh) to cut
down on inbox spam, also fixed prior bug where generated files had bad
paths in their #includes. removed namespacing option from gdbus-codegen
as linked objects do not run into naming conflicts as the previous
commits did. regenerate all genfiles (src/interfaces/foo/foo-gen.{c.h})
accordingly.