Suffix visitor

[mausch]

Now that #1089 is solved, we can include the suffix visitor I was talking about in that issue.
This is safer and more clear than using the current SuffixExtensions.Suffix because it only applies to Expression<Func<T, object>> instead of any object.
It also allows me to build a list of fields (of type Expression<Func<T, object>>) and apply a suffix to that whole list (useful for mapping multiple string fields with multiple analysers).

// put this anywhere you want
public static Expression<Func<T, object>> AppendSuffix<T>(this Expression<Func<T, object>> property, string suffix)
{
    var newBody = new SuffixExprVisitor(suffix).Visit(property.Body);
    return Expression.Lambda<Func<T, object>>(newBody, property.Parameters[0]);
}

/// <summary>
/// Calls <see cref="SuffixExtensions.Suffix"/> on a member expression.
/// </summary>
private class SuffixExprVisitor : ExpressionVisitor
{
    readonly string Suffix;

    public SuffixExprVisitor(string suffix)
    {
        Suffix = suffix;
    }

    protected override Expression VisitMember(MemberExpression node)
    {
        return Expression.Call(typeof(SuffixExtensions), "Suffix", null, node, Expression.Constant(Suffix));
    }

    protected override Expression VisitUnary(UnaryExpression node)
    {
        // allow rewriting child expressions
        return node;
    }
}

[gmarz]

Great stuff, thanks @mausch ! Will look into implementing this in the next few days.