Prepares preface for O'Reilly early release

* Describes who the book is for
* Corrects authors job titles as needed
* Provides an introduction to OpenStack
* Gives an overview of the organization and what you get out of
  each chapter
* Fixes a typo in Tales appendix
* Removes "What's Next" as a separate chapter and puts it into
a note at the end of Architecture chapters

Change-Id: Ib1f2a4012d09a4d3ff7885c95bbf165f2ef6d30f
Merge "Prepares preface for O'Reilly early release"