_timezone accepts an IANA timezone name, such as
"UTC", and applies it to both reads and writes.

For writes, time.Time values are converted to the
target timezone before formatting.

For reads, timezone-less strings are interpreted
as being in the target timezone.

Supporting configuration at the DB driver level
helps avoid industrial accidents when working with
SQLite datetime strings, which lack time zones.

So that time.Times may be formatted identically to how SQLite
does it natively with datetime and CURRENT_TIMESTAMP.

add _timezone DSN query parameter

See merge request !94

add _time_format=datetime support

See merge request !95