Add support for the rest of the simple types and yamls

[westonpace]

At the very least we should be able to import all of the standard YAML files. We are currently only importing a subset and already getting warnings for unsupported types:

warning: Ignoring impl with unrecognized type in YAML file: interval_day
warning: Ignoring impl with unrecognized type in YAML file: interval_year
warning: Ignoring impl with unrecognized type in YAML file: timestamp
warning: Ignoring impl with unrecognized type in YAML file: timestamp_tz
warning: Ignoring impl with unrecognized type in YAML file: date

In addition to rounding out support in funcgen we should make sure we have appropriate type builder methods for these types too.

Note that simple here means "not parameterized" simply because we have #3 for parameterized types. If #3 is already completed then we can go ahead and add support for parameterized types here too.