API to compare actual schema with code-generated schema

The `org.jetbrains.exposed.sql.SchemaUtils#createMissingTablesAndColumns` method helps to make sure the schema is correct and to convert it to achieve the goal.

Sometimes it makes sense to have more detailed manual converters for the database. The problem right now is that one cannot check if the converters sequence turned a database to be the same as the current schema.

It looks like the `org.jetbrains.exposed.sql.SchemaUtils#createMissingTablesAndColumns` method has enough to be turned into such an assertion method, e.g. `assertSchemaIsCorrect`