XNAT-2842: Fixed quotes in string building.
XNAT-2822: Updated to better handle assessor data not organized within an 'ASSESSORS' directory for the assessed session.
Merged in joelbalestra/xnat_builder_1_6dev_filelistfix (pull request #70)

XNAT-2822: Updated to better handle assessor data not organized within an 'ASSESSORS' directory for the assessed session.