Refactor the generation of docbook data
Refactor the generation of docbook data

Avoid duplicated data (mainly headers and footers for table files).

Also reformat the generated output to avoid having too much white
spaces.

Change-Id: Ib7ff29ae6d3180a401c5cac482e82a56997751a7

savinash47/openstack-doc-tools,openstack/openstack-doc-tools,savinash47/openstack-doc-tools,savinash47/openstack-doc-tools,openstack/openstack-doc-tools