Support one sided navigation properties

[christophano]

Hi, I'm having a problem with my model, which makes use of one sided navigation properties, which doesn't seem to be supported. For example;

class Foo
{
    public int Id { get; set; }
    public int BarId { get; set; }
    public virtual Bar Bar { get; set; }
}
class Bar
{
    public int Id { get; set; }
}
class Context : DbContext
{
    void OnModelCreating(ModelBuilder builder)
    {
        builder.Entity<Foo>()
               .HasOne(f => f.Bar)
               .WithMany()
               .HasForeignKey(f => f.BarId);
    }
}

I have added support for this, if you accept pull requests.

[dbroudy]

Thanks for the PR @christophano I'll take a look at it this weekend.