Improved pattern language cheat sheet, added math evaluator cheat sheet

include/views/view_help.hpp

@@ -27,9 +27,11 @@ namespace hex {
     private:
         bool m_aboutWindowOpen = false;
         bool m_patternHelpWindowOpen = false;
+        bool m_mathHelpWindowOpen = false;
 
         void drawAboutPopup();
         void drawPatternHelpPopup();
+        void drawMathEvaluatorHelp();
     };
 
 }