Reworked pagination for better performance (at least in Lucene queries)
Added NonRootObjectException in these operations in DataProvider:
 - getGraphByObjectId
 - getRelatedObjectsById
 - getPathById
 - mergeObjects
 - splitObject
 - getDocumentsContainingObjectById
 - getFilteredDocumentsContainingObjectById
Fixed save with joined objects
Added locking in service methods which modify db
Merge remote-tracking branch 'origin/server-impl'