Updating comments per the C++ core guidelines and removing trailing whitespace (#194)

Fixed comments that were inconsistent with the style guidelines described in C++ core guidelines and the modern C++/WinRT language projections and removed trailing whitespace.

Inserted a space after the beginning of the comment so the text wasn't touching the // on all occurrences.

Removed all occurrences of trailing whitespace

src/Calculator/Converters/BooleanToVisibilityConverter.h

@@ -16,7 +16,7 @@ namespace CalculatorApp
         public:
             static constexpr Windows::UI::Xaml::Visibility Convert(bool visibility)
             {
-                return visibility 
+                return visibility
                     ? Windows::UI::Xaml::Visibility::Visible
                     : Windows::UI::Xaml::Visibility::Collapsed;
             }