Add Ceilometer Admin guide chapter to OS manuals

Add the chapter file and the corresponding entry in
bk_admin_guide_cloud.xml. for initializing the Telemtery chapter.
Also add the skeletons for the main sections. The content will be
added in dependent patch sets.

Implements: blueprint add-ceilometer-admin-guide-to-openstack-manuals
Change-Id: I99bd13faee0f92cd9688a180acbe10bb9d0a8f13