Refactor API endpoints for starting Sense tasks

[mountaindude]

Is your feature request related to a problem? Please describe.
The API for starting Sense tasks is very useful and flexible, but that flexibility has resulted in some inconsistencies around how parameters are handled in different usage scenarios.

Specifically:

• The returned JSON objects should be consistent across all usage scenarios. "Invalid", "denied" should always mean the same thing.
• If all tasks are passed in the message body, the magic task ID of - can be passed in as task ID in the URL. This already works to some degree, but is not consistent.
• Create test cases for all major usage scenarios. Document in Google doc/Excel files.