Support for [List] field

Added support for list fields.
Example usage within a viewer or other graph type:

[List]
public ListField<EntityA> EntityList => (context) =>
{
    return new List<EntityA>()
    {
        new EntityA { Id = new Guid(), Name = "No1" },
        new EntityA { Id = new Guid(), Name = "No2" }
    };
};