Source generate NeedsUpdate and NeedsFrameUpdate for entity systems

[DrSmugleaf]

I want those 100 milliseconds (on debug) back seymour

Draft because it needs to force EntitySystems to be partial first (otherwise if you inherit partial A without update methods to non-partial B, the game will think B has no update methods)
To test:

public partial class A : EntitySystem;

public sealed class B : A
{
    public override void Update(float frameTime)
    {
        base.Update(frameTime);
    }

    public override void FrameUpdate(float frameTime)
    {
        base.FrameUpdate(frameTime);
    }
}