Update EnginioClient docs

Change-Id: Id75b5652110f3d74bd72149085bf847eef018ad8
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Fix some random qdoc problems

Change-Id: I65967c42cbb2523e37399eda33169b1922bd1bfc
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Use lower case for "backend id" in documentation.

Change-Id: I2f5384c8f9b466339b2de5cc896c5af90b209c13
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Remove unsued variable

Change-Id: I16f38c1e9d104209870dfa54ee392aedb792ffe3
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>