columnToFieldIndex: revert b5ce3b9 change, as it breaks tag mapping when a field marked transient matches a column mapped to another field.  Fixes #175 but reverses #146
TestSelectAlias: modify to demonstrate how this behavior can be achieved using two separate structs - one that reflects the actual table structure (for inserts/updates) and one with the extended field, which can be used for selects.
Add database/sql Db.Prepare & Transaction.Prepare equivalents
Make Prepare test dialect agnostic

The 'true' literal doesn't play well with some SQL dialects