Move Lexer to u16string handling, for unicode support

src/Parser/ParsedExpressions/ParsedExpression.hpp

@@ -100,7 +100,7 @@ public:
 };
 
 class LiteralStringExpression : public ParsedExpression{
-    const string _value;
+    const u16string _value;
 public:
     const ParsedExpressionKind GetKind() const final{
         return ParsedExpressionKind::LiteralString;
@@ -111,7 +111,7 @@ public:
     {
     }
 
-    const string& GetValue() const{
+    const u16string& GetValue() const{
         return _value;
     }
 };