Use configure option yaml path to generate elog-errors.hpp

Add a config variable that can be passed via a recipe to
point the parser to a directory where the error yaml files are.
Rename elog-gen.hpp to elog-errors.hpp, which better matches the
exception error log file names.
Include elog-gen.hpp in elog.hpp so that callers that need to
create and commit error logs only need to include one header file.

Change-Id: Ie3cd65ac761c1f7b2c99c50a2273859283a5ab4b
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
6 files changed