Implement basic support for numeric and date range types

[Ragnis]

• The Int32Range and Int64Range can be used for reading/writing int4range and int8range values, respectively
• The Float64Range is useful for reading/writing numrange values, when possible loss of precision is not of concern.
• The DateRange type can be used with the Postgres daterange type. This is the only one that currently supports infinite values.

I'm not yet sure what would be a good way of handling the numrange type. Maybe by treating the min/max values as strings?

[arp242]

I'm closing this in favour of #1196, which seems a better solution using type parameters.