Modify the documentation source in order to refactor the 3scale library titles

This is the task to implement the redesign of the 3scale docs library. The primary focus of this update will be on rearranging content and moving it around between books (e.g. editing master.adoc files). The individual topic files should be changed as little as possible. A minimum amount of editing of topic files will probably be necessary, however. For example, to update cross-references and links.