Add documentation for the library interface

This commit adds documentation for the library interface, formerly
known as tempest-lib, and the release versioning.

Partially implements bp tempest-lib-reintegration

Change-Id: I623222a17fe3563bbe767fa803e8f771a21687a1
diff --git a/doc/source/index.rst b/doc/source/index.rst
index 32e6e51..17def1c 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -11,6 +11,7 @@
    HACKING
    REVIEWING
    plugin
+   library
 
 ------------
 Field Guides