public / sequelize

query-interface tests make stronger assertions

* all tests covering functionality which modifies schema
  now verify that the schema has actually changed, instead of
  just verifying against the number of logs output
* remove assertions against sql count in query-interface.test
* remove unused rawSelect against table in test

Fixes required for new query-interface tests for PG / MySQL / MariaDB

* PG: changing a column to DataTypes.FLOAT results in it being stored (and
  returned as) 'DOUBLE PRECISION'
* ensure that test schema is torn down after each test, to avoid tests
  interacting with each other
* remove unneeded calls to dropAllSchemas in query-interface.test.js
  - this is done in the afterEach call now
* MySQL/MariaDB: we have to change our expectation depending on the
  dialect, as the DataTypes names are too inconsistent