Added ability for admin to manually verify a user account
XNAT-2338: Worked around NPE to check for null value and let HTTP status set in getFileWriters() stay.
XNAT-2272 Added a clause to filter out empty resource folders when downloading via the File Manager.
Merged in mhileman/xnat_builder_1_6dev_verifyaccount (pull request #76)

Added ability for admin to manually verify a user account