Updated README to include some quickstart information and information on
what YAQL is.
Includes stubs for further expansion of YAQL documentation and proposes
general structure of how YAQL documentation might look like.
Targets blueprint: yaql-docs
Change-Id: I65885bd132bb3efa5798aa0cb6f1774b2348a44e
(cherry picked from commit f134c743b0)
517f80e03c