Support for the V ORM

[elliotchance]

DO NOT MERGE.

This is partial support for the ORM. However, there are some challenges that need to be addressed before this can be properly reviewed and landed:

1. The ORM in V requires drivers to be hard-coded. See #90.

2. The Connection doesn't really implement orm.Connection because the vsql Connection is required to be mut and the current interface definition does not allow this.

3. We need to create a new test suite for the ORM. vsql/orm_test.v filled with combinations of statements "sql" commands will work just fine. Specifically, we need to test different combinations of expressions and types.

Fixes #90

[N0tExisting]

You can set this PR to a draft, so it can't be merged