no longer redefine ad_conn in install since it's needed in some libraries in callbacks, do install.xml after admin user created, load catalogs after install.
Adds a public interface apm::process_install_xml to use install.xml files subsequent to the bootstrap, change bootstrap to use the provided api, adds install::xml namespace + functions to support the various xml stanzas (such as set-parameter or set-join-policy) and a clean extension mechanism via functions in the install::xml::action:: namespace. Thanks to Lee Denison for cleaning up and extending the existing install functionality.