[SDL 0011] iOS Library RPCs conform to NSCopying

[theresalech]

Proposal: iOS Library RPCs conform to NSCopying

This proposal is to make all RPC requests, responses, and structs conform to the NSCopying protocol and for all requests containing structs to hold those properties with the copy modifier. This is a minor change, as the public interfaces for the RPCs will change to support the copy method.

Review: smartdevicelink/sdl_evolution#33

Steering Committee Decision:

This proposal has been accepted. There was discussion around the necessity of doing so, but the eventual decision was that allowing model objects to be copied is a common practice, so even if we don't immediately begin copying these objects, we should support the ability to do so.