raise NOT_FOUND error if file does not exist
Merge pull request #1 from qcode-software/db_file_thumbnailer_404

raise NOT_FOUND error if file does not exist
sql_where_or bug fix
Revised sql_where_or tests
Merge pull request #2 from qcode-software/sql_where_or_bug_fix

Sql where or bug fix
Merge sql_where_or bug fix into qcode-3