Add support for the default string formats

[jbowes]

A user can configure custom string formats to convert string types to other types based on the defined format, but the default defined formats are not supported.

They should be included out of the box, but overridable by user configuration.

This should look something like:

• define a map of default format names to their types in translator
• when executing, merge this into the user's supplied configuration, preferring the user's values.