Create Toolkit as a Universal Framework

[boland25]

Feature description
The idea would be to able to combine the iOS and macOS into one universal framework through the use of xcframeworks or swift package manager. As of XCode 12 SPM says its able to handle binary and binary dependencies so that might be the best way to go.

Acceptance criteria

1. As a Developer, when I want to add helib to my project, go to FIle > Swift Packages > Add Package Dependency.
2. Enter into the textfield our git clone url, and get helib added as a framework dependency to the developer's project

[boland25]

So this is successful as a Swift Package that relies on dependencies that are binary frameworks. I can make it work when I create NTL and GMP as .xcframeworks that wrap the binaries. Once this is up and running we will need to decide on a place to store the package information as well as the pre-built binary dependencies. Then we will need to re-configure our toolkit to load the HELib libary as a package dependency.