documentation: Title changes

Removed "The" from all the titles of the books.  This makes it easier
to reference to them and easier for the automated processing of the
mega-manual.

(From yocto-docs rev: af566d6d007cff642648698ea487a6eeaa8cc930)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>