Removed (deprecated in 0.14, BACKLOG #67):
- POST /execute_sql_from_file and /execute_sql_with_parameters_from_file;
  /q/{name} runs the same saved query.
- Importing the pre-SQLite JSON files. A home whose data is only in them
  (0.10 or older - 0.14's notice said 0.9) is refused at startup with
  what to do: start 0.14 on it once. Leftover or empty files are ignored.
  The deprecation mechanism stays, tested with a temporary deprecation.

Release: version 0.15.0; CHANGELOG's Unreleased becomes 0.15.0 with
"Upgrading from 0.14"; SQLite and PostgreSQL upgrade fixtures for 0.15.0
(the 0.7-0.10 fixtures now check the refusal); openapi.json regenerated;
BACKLOG sequence updated.