Update the first fixture to use new constraints key.

Many more fixtures will need to be updated.
Use RESTART IDENTITY

It is far less janky than trying to guess sequence names.
Fix errors when columns match value lengths.
Add a method to get the schema collection.

This makes mocking simpler, and doesn't force callers to construct
a Schema\Collection making a hard dependency.
Multi-row insert's do not work in Sqlite right now.

I've fixed some of the issues but not all of them. There is
still a problem with nulls being inserted in every column.
Update usage of Query() class and fix insertion errors.

Fix errors inserting records (there are still remaining issues with
SQLite).
Make fixtures work again.

New style static fixtures now work in MySQL.
Remove resetSequence()

The only driver that needed it was postgres. However, using truncate
with RESET IDENTITY will force automatically reset the related
sequences.
Fix incorrect constant + method name.

I missed this when I changed things around.
Implement simple schema import.

I've removed model + record imports as models are no longer used to do
imports, and I feel record imports were an infrequently used feature.
Add missing docblock.