Not meaningful error in case of options with same name

Repro:
```csharp
class Options {
[Option('s', "storage", Required = true, HelpText = "Storage account name hosting metrics")]
public string StorageName { get; set; }

[Option('s', "key", Required = true, HelpText = "Key of given storage account")]
public string StorageKey { get; set; }
}
```

Error given is:
`System.InvalidOperationException: 'Sequence contains more than one matching element`

Suggested message:
`One of more options has the same name. Check attributes properties`

Thanks :)