Update autogenerate-config-docs for openstack-doc-tools

Let's keep the flagmappings as part of openstack-manuals and the
tool itself in openstack-doc-tools.

This patch removes the tools and updated the documentation.
A corresponding patch for openstack-doc-tools will be done.

Change-Id: Iad8f0607af9ff8522e6d7567cfa685301813ecfe
Merge "Update autogenerate-config-docs for openstack-doc-tools"