1. Updated poky.ent to contain 2.1.3 variables
2. Updated mega-manual.sed to use "2.1.3" string
3. Updated all Manual Revision tables to use "May 2017" date
(From yocto-docs rev: 49e08a543347d7e6548f6873faf701a0e5e95ae8)
Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>