Support Execer interface for non-parameterized commands
Don't assume only one generated id per row in execute
Unify attribute names: affected_rows -> rows_affected
Ensure rows_affected >= 0 also for nuodb_execute
Don't return ResultNoRows unless rowsAffected == 0

This allows extensions in the NuoDB command API
Comply with the connection timezone parameter

- Also compares time.Time instances with Equal as they should be