GraphAsynch Improved implementation
Merge branch 'develop' of https://github.com/orientechnologies/orientdb into develop
Removed old replica method
Removed unnecessary check
OrientAsynchGraph: removed locking
Issue #2721: support merge of keys

-  created new RECORD_REPLACED mode in Hooks to avoid Duplicated Record
Exception from indexes
- create unique indexes with optional setting (in metadata):
mergeKeys=true
Merge branch 'develop' of https://github.com/orientechnologies/orientdb into develop
Issue #2721: supported merging on OConcurrentModificationException