CheckpointServiceMemory renamed to MemoryCheckpointService
Introduced TimeoutType enumeration
Fixed placement of checkpoints sets/removes in GeneralTaskBackend
Refactoring RetryPolicy: delete usage ActorRuntimeException.
Merge branch 'refs/heads/feature/retrypolicy' into develop
Refactoring of Checkpoint service and entities
Refactoring of task start_to_close expiration recovery service
bugfix at checkpoint service
Minor enhancements
Enhancements and bugfixes for Expired task recovery service
Merge branch 'develop' of https://github.com/taskurotta/taskurotta.git
into develop

Conflicts:
	wf-server/src/main/java/ru/taskurotta/server/recovery/TaskExpirationRecovery.java
Refactoring ErrorContainer
Merge remote-tracking branch 'refs/remotes/origin/develop' into develop
Added some checkpoints checking/unchecking for backends
Merge branch 'develop' of https://github.com/taskurotta/taskurotta.git into develop
fixed MemoryQueueBackend synchronization issue
Removed unused (de)serialization classes
Example reconfigured for retry policy
Merge remote-tracking branch 'origin/develop' into develop
Refactoring LinearRetryPolicy.java
some code cleanup
Recovery processes refactor
Extract interface TaskOptions.java from implementation TaskOptionsImpl.java
Add support different signature in same method in client interface