Replace class Aaa with something resembling real-world code

[rdeago]

Reference version

2.0.1-preview

Background and motivation

See #17

Proposed enhancement

A possible addition could be a simple Calculator class with methods like Add, Subtract, etc.

Viable places to look at for additions may be articles about unit testing, C# tutorials, etc.

Implementation proposals

Just some quick guidelines:

• Don't add anything involving UI and/or I/O.
• Add a dependency to PolyKit.Embedded to test how coverage tools etc. react to it;
• Only other allowed dependencies (at least for now): Microsoft extensions, Microsoft polyfills (System.Memory etc.), plus our own L.o.U.I.S. as soon as it is released.

Usage examples

n/a (depends upon the actual additions)

Risks

As already pointed out in #17, the removal of class Aaa is a breaking change, but no one is going to complain about it.

Additional information

@ric15ni I'm fine with the same PR closing this issue and #10 together.