Add overload of GetValue to set default value

[bjarnef]

It would be nice to have an overload of GetValue<T>()

LeBlender/Src/Lecoati.LeBlender.Extension/Models/LeBlenderValue.cs

Lines 36 to 54 in 09fb8f8

	public T GetValue<T>(string propertyAlias)
	{
	var property = GetProperty(propertyAlias);
	if (IsEmptyProperty(property))
	{
	return default(T);
	}
	if (property.Value is long)
	{
	int newValue;
	if (Int32.TryParse(property.Value.ToString(), out newValue)) {
	property.Value = newValue;
	}
	}
	return property.GetValue<T>();
	}

var text = item.GetValue<string>("text", "No description")
var numberOfNewsItems = item.GetValue<int>("numberOfNewsItems", 3)

so you can set default value, like in Umbraco core:
https://github.com/umbraco/Umbraco-CMS/blob/5397f2c53acbdeb0805e1fe39fda938f571d295a/src/Umbraco.Web/PublishedContentPropertyExtension.cs#L19-L22