Convert getter-only properties to expression-bodied members

Getter-only properties with a single return statement can be converted to expression-bodied members. This is an improvement to CC0038 (related to #101).

This

    public double Area
    {
        get { return Width * Height; }
    }

becomes 

    public double Area => Width * Height;

Also, the codefix was in the namespace CodeCracker.Style.Style (notice the extra .Style).