Prototype code for packet handler decorators

[snarlynarwhal]

I wanted to get feedback before continuing with the last step of wiring up the decorators.

I added 3 classes to Networker:

• DecorateAttribute - Helper attribute to assign decorators to handlers
  • Example: Decorate[typeof(AuthorizationHandlerDecorator)]
• DecoratorAttribute - Base attribute class for making custom attributes to assign decorators
  • Example: [Authorize]
• PacketHandlerDecorator

The attributes can get added to handlers and modules.

I put together Demo.Decorators to demonstrate how the features gets used. It does not function yet.

The last part I need to do is wire up the decorators on startup. Should do this in BuilderBase.SetupSharedDependencies?