Recover from HDFS FileSystem handle being closed
Merge pull request #74 from Erwa/li-emails-only

Fix for Issue #73: Added email address domain validation; also changed error message to show all validation errors instead of just the first one; also added examples to help text under access list and notification list fields
Merge pull request #78 from Erwa/hdfs-delete-concurrency

Recover from HDFS FileSystem handle being closed