Add support for phases
This adds a "publish" permission level (between "init" and "write") required to
be able to change the phase of a changeset from "draft" to "public".
Update documentation accordingly.
This is meant to be used for using the changeset evolution feature of mercurial,
see http://evolution.experimentalworks.net/doc/
init user=root/**
deny repo=hgadmin
write user=users/**