Add submission delete endpoint

[pkalita-lbl]

Fixes #1165

• Adds a handler for DELETE /api/metadata_submission/{id} requests. I figured that only owners (or admins) should be able to delete submissions. I also erred on the side of caution in not allowing the delete if the submission is locked by someone. If you think that could be better let me know.
• Sort of unrelated, but it would be really helpful to the Field Notes app if the submission list endpoint had a stable sort. I know there have been discussions in the past about full on sorting and filtering of submissions in the portal. But without getting into all that I thought it might be uncontroversial to just sort them by newest by default.

[naglepuff]

• Sort of unrelated, but it would be really helpful to the Field Notes app if the submission list endpoint had a stable sort. I know there have been discussions in the past about full on sorting and filtering of submissions in the portal. But without getting into all that I thought it might be uncontroversial to just sort them by newest by default.

This seems reasonable to me. Is there an existing issue documenting this that will be closed by this PR?

[pkalita-lbl]

• Sort of unrelated, but it would be really helpful to the Field Notes app if the submission list endpoint had a stable sort. I know there have been discussions in the past about full on sorting and filtering of submissions in the portal. But without getting into all that I thought it might be uncontroversial to just sort them by newest by default.

This seems reasonable to me. Is there an existing issue documenting this that will be closed by this PR?

No, just something that's been lingering the back of my mind

[naglepuff]

Thanks!