update changelog for v1.2.15
update changelog for v1.2.15

screenconcept/qbrick,brandleadership/kuhsaft,brandleadership/qbrick,screenconcept/qbrick,screenconcept/kuhsaft,brandleadership/qbrick,screenconcept/kuhsaft,screenconcept/qbrick,brandleadership/kuhsaft,brandleadership/qbrick,brandleadership/kuhsaft,screenconcept/kuhsaft