Add concept of foreign key translation

[DominicWatson]

i.e. there is an external system, with its own IDs, it would be awesome if the API handled translating those IDs into and from Preside PKs when pushing and pulling data from the API. Configuration could be like:

/**
 * some_object.cfc
 * 
 * @dataApiExternalIdField external_id;
 */
component {
    property name="external_id" type="numeric" uniqueindexes="externalId" required=false;
}

Then, in an object that references the above:

/**
 * another_object.cfc
 * 
 */
component {
    property name="some_object" relationship="many-to-one" relatedto="some_object" required=true dataApiTranslateFk=true;
}

API calls by the external system would then need only use their own key values for the relationship object and would only receive those keys in return.