Add check that only 1 jO file is in a DSID directory

Changes introduced

Add check in check_added_files that only 1 jO is present in each DSID directory.

Tests

Added 800xxx/800000/mc.test.py and run

./scripts/check_added_files.sh 
Find files that have been added in last commit...
OK: file: 800xxx/800000/mc.test.py in white list
ERROR:        2 jO files found in 800xxx/800000

Issues resolved

Closes #85 (closed)

/label new feature