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/Controls/OverflowTextBlock.h

@@ -12,7 +12,7 @@ namespace CalculatorApp
         public ref class OverflowTextBlock sealed : public Windows::UI::Xaml::Controls::Control
         {
         public:
-            OverflowTextBlock() 
+            OverflowTextBlock()
             {
             }