Another round of Pillar work to support Ask

[jde]

Bugfixes

• [x] Fix missing dates on Form
• [x] Look into this issue:

"DELETE", "/api/form_submission/{id}
{
  "error": {},
  "message": "Error deleting Search [ObjectIdHex(\"5755caf79d913a0006bf26b2\")]",
  "code": 500
}

Misc

• [x] Make endpoint more explicit:

/api/form_galleries/{form_id} is concise but requires knowledge of relationships
/api/form_galleries/form/{form_id} is more verbose but explicit