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/FlipButtons.cpp

@@ -43,7 +43,7 @@ void FlipButtons::OnKeyUp(KeyRoutedEventArgs^ e)
 }
 
 void FlipButtons::OnButtonIdPropertyChanged(
-    NumbersAndOperatorsEnum /*oldValue*/, 
+    NumbersAndOperatorsEnum /*oldValue*/,
     NumbersAndOperatorsEnum newValue)
 {
     this->CommandParameter = newValue;