Update MetaData to include subproIsRecurringOrder in Basket object

[chrismshea]

Fixed in PR #82

Issue

When recurring orders are placed the c_subproIsRecurringOrder field is sent as true, but it is not being stored on the basket.
This causes issues because the order if successful does not include the flag indicating it as a recurring order, and additionally the flag cannot be used to identify it as a subscription order when applying promotions or special handling for Subscription orders.

Resolution

Include the below attribute definition in the Basket object in the metadata site_import.

            <attribute-definition attribute-id="subproIsRecurringOrder">
                <display-name xml:lang="x-default">Subpro Is Recurring Order</display-name>
                <type>boolean</type>
                <localizable-flag>false</localizable-flag>
                <mandatory-flag>false</mandatory-flag>
                <externally-managed-flag>false</externally-managed-flag>
            </attribute-definition>