[master] Fix scripts

Few scripts improvements

• Add information to result if no ancestor is found (fixes https://its.cern.ch/jira/browse/LHCBDIRAC-735)
• Add switch --NoDirectories to list-directory in order to not list the subdirectories
• Reset tasks rather than files is a task is Submitted without an ExternalID
• Fix creation of run ranges when getting run information items per run range
• Add sphinx compatible doc-strings in ScriptExecutors (BK)