show async decorator in toString()

Signed-off-by: Christian Lüthold <biocodr@gmail.com>
fix bug in AsyncComponent

Signed-off-by: Christian Lüthold <biocodr@gmail.com>
another bugfix

Signed-off-by: Christian Lüthold <biocodr@gmail.com>
remove unused code

Signed-off-by: Christian Lüthold <biocodr@gmail.com>
async execution/rollback exception handling tested

Signed-off-by: Christian Lüthold <biocodr@gmail.com>