[OPENENGSB-3664] implemented context based concurrency management for the persist interface
[OPENENGSB-3664] started writing tests for the new feature
[OPENENGSB-3664] changed the implementation to a better way, added more tests
Merge pull request #865 from Arcticwolf/OPENENGSB-3664

[OPENENGSB-3664] concurrent write protection for the PersistInterface