Csvhelper: Parsing error messages

I saw a pull request that should address issue of clarifying error messages, but it still would not provide enough flexibility.

Currently I have to write something like this in order to provide to the user a better level of details about error:

``` c#
var e = new List();
csvReader.Configuration.ReadingExceptionCallback = (ex, row) =>
{
foreach (var error in ex.Data.Values)
{
var info = error.ToString().Split(new[] { "\n", "\r\n" }, StringSplitOptions.RemoveEmptyEntries);
var value = info[4].Split(':')[1].Trim();
var field = info[3].Split(':')[1].Trim();
e.Add(string.Format("Could not read value {0} in row {1}, field {2}.",
value, row.Row, field));
}
};
// return e to the webpage (for example as JSON)

This is relatively ok. It gives information where exactly parsing error has occured. However, as you can see, digging this information is ugly since I have to parse string to get the value and the field name. It would be nice if this information could be exposed via properties so that I could write something like this:

``` c#
csvReader.Configuration.ReadingExceptionCallback = (ex, row) =>
{
    foreach (var error in row.Errors)
    {
        e.Add(string.Format("Could not read value {0} in row {1}, field {2}.",
            error.Value, error.Row, error.FieldName));
    }
};

But above is ok... it works. What's more important is the following request.
It would also be nice to be able to provide information WHY parsing failed.
Let's say a field only accepts values "Red" or "Blue", but user types in "Yellow". We could solve this by:

c# // in the MyClassMap : CsvClassMap<MyClass> class Map(x => x.Color).ErrorMessage("Accepted values are 'Red' and 'Blue'"); ... // in the ReadingExceptionCallback e.Add(string.Format("Could not read value {0} in row {1}, field {2}. {3}", error.Value, error.Row, error.FieldName, error.Message));

This syntax would provide a lot of flexibility for developer and give clear feedback to the user.

Let me know your thoughts.