* Calc.csproj:
* CalculatorEngine.cs: added calculator engine

* NumericInputBuffer.cs: was NumericEntryMediator the name never made
  any sense

* TestCalculatorEngine.cs: fixed calculator engine

* TestNumericInputBuffer.cs: renamed from TestNumericEntryMediator

* TraditionalCalculator.cs: handled rename NumericInputMediator

* SkunkTest.csproj: added tests for CalculatorEngine


* TestNumericEntryMediator.cs: renamed to match related file

* NumericEntryMediator.cs: renamed to NumericInputBuffer