[LMS-2301] example reporting and processing scripts + simple handler and a validator

datastore_server/resource/examples/data-set-handler.py

...tore_server/resource/examples/data-set-processing-mail.py

datastore_server/resource/examples/data-set-processing.py

...re_server/resource/examples/data-set-reporting-content.py

...ore_server/resource/examples/data-set-reporting-search.py

datastore_server/resource/examples/data-set-reporting.py

datastore_server/resource/examples/data-set-validator.py