add the ability for modules to be used as value/overlay sources

this PR enables modules (specified in qualified form:  "package1.package2.module", or as instances of types.TypeModule).   

This also gives configman the ability to write modules with "--admin.print_conf=py"  


Is my concern still valid though? (editing the generated file some day will edit all lines when it auto-detrails). 
We could easily fix it with `'\n'.join(x.rstrip() for x in json.dumps(thing).splitlines())`
Is it worth it?