* Transformed the test database to match the new data model. Added
``ts_ext_data`` table and moved ``ts_user.ext_data`` values to it.
* Added D0022: cascade delete ``ts_ext_data`` when ``ts_entry`` record is
deleted.
* Completed refactor of ``ts_api`` functions to account for extended data:
* ``post_entry/3``
* ``put_entry/3``
* Created ``ts_entry:write/2`` to write extended data atomically with the entry.
* Fixed copy/paste bug in ``ts_ext_data:create_table/1``.
* Fixed implementation of ``ts_ext_data:set_property/3`` to be explicit about
taking a record, not a reference. It then extracts the reference and passes it
to the underlying implementation in ``ts_ext_data:do_set_property/3``.
* Refactored ``ts_ext_data:do_set_property/3`` to take a record *reference*, not
the record itself.
* Refactored the ``ts_ext_data:get_property/2`` and
``ts_ext_data:get_properties/1`` functions to return key value tuple pairs,
not ``ts_ext_data{}`` records.