[poincare] Clean Expression and Layout builders

Before: Opposite(Opposite(Rational(1))) misleadingly created the
expression "-1"; now, Opposite::Builder(Opposite::Builder(Rational(1)))
creates "--1"

poincare/src/function.cpp

@@ -105,7 +105,7 @@ Expression Function::replaceSymbolWithExpression(const SymbolAbstract & symbol,
     value = value.replaceSymbolWithExpression(xSymbol, xValue);
     Expression p = parent();
     if (!p.isUninitialized() && p.node()->childNeedsParenthesis(value.node())) {
-      value = Parenthesis(value);
+      value = Parenthesis::Builder(value);
     }
     replaceWithInPlace(value);
     return value;