Brainstorm on productization for iOS and specifically for distribution of libs

[atsakiridis]

This is just a 'container' for some thoughts as a base for future discussion, as at some point this will become critical.

See #601 for some problems we have currently.

In a nutshell CocoaPods has come with its share of problems. At some point in the future we need to think this through and come up with a robust & complete solution. Some points very quick:

• Apart from CocoaPods there is also Carthage, but not without it's share of issues
• Apple seems to be backing a swift package manager, finally. However it seems pretty new, so we need to wait and see if it can become helpful in the future and how it supports objective-C codebases.
• Another way to go, is to come up with build facilities to automatically come up with a single iOS framework containing all of SDK library code, Sofia Sip, WebRTC and exposing headers just for the SDK library.