Generate mid level apis

[sbrossie]

The api generation will generate at most two api methods for each endpoint:

• One method with minimal number of arguments -- removing params with a default value set on the server side, and matching such default values.
• One method with all arguments -- the previous one calls this one specifying default values when this apply.

There is no convenience middle methods between the two, leaving the user to enter possibly lots of null values, ...

Example: Creating a payment method will look like the following:

final PaymentMethod paymentMethodCC = accountApi.createPaymentMethod(paymentMethodJson, accountJson.getAccountId(), true, false, NULL_PLUGIN_NAMES, NULL_PLUGIN_PROPERTIES, requestOptions);

It might be nice to have methods that don't require plugin names, plugin properties, audit logs, ...