Locking destinations and old parents when moving objects and removing them from their parent.  No longer creating MD_CONTENTS during move when one doesn't exist.
Locking for delete and metadata operations.  Split locking functionality into a separate class so it can be reused outside the digitalObjectManager
Bulk updating premis after move operations in a separate thread.  Locking on premis updates
Clearing unlocked pids from map if there is no one waiting to use them
Merge pull request #165 from UNC-Libraries/move-concurrent

Move concurrency