Update datetime format and use UTC everywhere

api/api_specification.md

api/api_specification_template.md

api/src/api/authentication.py

api/src/api/routes/job.py

api/src/api/routes/stats.py

api/tests/routes/feedback.py

api/tests/routes/object_modifications.py

api/tests/routes/stats.py

...n_py/src/videoag_common/api_object/fields/basic_fields.py

common_py/src/videoag_common/miscellaneous/__init__.py

common_py/src/videoag_common/miscellaneous/mail.py

common_py/src/videoag_common/miscellaneous/util.py

common_py/src/videoag_common/objects/site.py

common_py/src/videoag_common/test/object_data.py

job_controller/jobs/media_process_scheduler/job.py

job_controller/jobs/source_file_sorter/job.py

job_controller/jobs/view_stats_aggregator/job.py

.../src/job_controller/executor_api/local_docker_executor.py

job_controller/src/job_controller/job_controller.py