Add STPBillingAddressFieldsName option for STPBillingAddressFields

[joeydong-stripe]

Summary

Add STPBillingAddressFieldsName option for STPBillingAddressFields so users can require just the name part of the billing address. The full set of options are:

typedef NS_ENUM(NSUInteger, STPBillingAddressFields) {
    /**
     No billing address information
     */
    STPBillingAddressFieldsNone,
    /**
     Just request the user's billing ZIP code
     */
    STPBillingAddressFieldsZip,
    /**
     Request the user's full billing address
     */
    STPBillingAddressFieldsFull,

    /**
     Just request the user's billing name
     */
    STPBillingAddressFieldsName,
};

Motivation

MOBILE-25

Testing

[joeydong-stripe]

r? @csabol-stripe / @danj-stripe

[danj-stripe]

LGTM

[joeydong-stripe]

thx