Add worker - support for background jobs/tasks.
Add client (frontend) for worker and make it configurable.
Extend worker to work with extension configuration.
fix CS issues
add some gearmand usage hint
allow for directory independend worker backend call

includes now prefixed with ONTOWIKI_ROOT
Extend default configuration file by Gearman/worker settings.
Catch job worker exceptions in backend.
Improve code style in worker backend.
add TestJob to log only
Compact interface of worker job registration.
Extend worker by server side logging.
Add new log level SUCC (8) for successfully handled jobs.
implement new interface
fix logger variable
Merge branch 'feature/worker' into develop