First draft release of SwiftAA 2! (alpha-0)

A whole world of modern expressive Swift code base giving access to most of the Astronomical Algorithms. Lots to be perfected, but that's time for a release, since most of the (Obj-)C++ code is now covered, and more importantly, elevated to a more expressive formulation.

A draft of a Swift Playground is also provided for those who wants to play with SwiftAA, to study solar system dynamics, and properties for instance.