* Migrated `AddressSectionElement` and friends to `StripeUICore` for use in Identity.
* Migrated `Array.stp_boundSafeObject` to `StripeCore` because this is used by `AddressSection` and it seemed like something we should make available to all of our modules (not just ones that use `StripeUICore`).
* Made title configurable in `AddressSectionElement` rather than hardcoding this to "Billing Address"
* Migrated the localized "Address" string to `StripeUICore` in anticipation for using it with the address section for Identity
* Updated path to `Resources` directory in `StripeUICore.podspec`
* Included Images for `StripeUICore` target in `Package.swift`
* Updated version of cocoapods to latest so installation tests would run locally
Created an empty `StripeUICore` module and enabled Carthage, CP, and SPM. There is currently no code in this module, other than a `Placeholder.swift` file.
Yuki Tokuhiro