Make synchronization service extendable, update userprojects model

so how do you make sure that you solution actually works the way you intended when it's integrated with the EDB?

I can guarantee you, it will fail as soon as an assignment is deleted once, because after that it will be permanently marked as deleted in the EDB.

see updateDeletedObjectsThroughEntityManager:
https://github.com/openengsb/openengsb/blob/master/components/edb/src/main/java/org/openengsb/core/edb/jpa/internal/AbstractEDBService.java

as for the second problem, correct, oversaw the + because there were too many + ;)