* Part 1: added limits feature to rusqlite dependencies.
* Part 2: replace references to SQLITE_MAX_VARIABLE_NUMBER with sqlite3_limit.
* Move assertion check for correct number of variables in repeat_values to before call as this is where the variable is defined.
* Part 3: add tests
* Add a failing test for EDN parsing '…'.
* Expose a SQLValueType trait to get value_type_tag values out of a ValueType.
* Add accessors to FindSpec.
* Implement querying.
* Implement rudimentary projection.
* Export mentat_db::new_connection.
* Export symbols from mentat.
* Add rudimentary end-to-end query tests.
