UTP: Separate Request types into classes

[ScottyPoi]

1. UtpSocket

• Refactors UtpSocket class into abstract class with shared logic
• Creates new classes ReadSocket and WriteSocket
• Separates methods and attributes of different types of sockets
• new constructor function createUtpSocket

2. ContentRequest

• Refactors ContentRequest class into abstract class
• Creates new class for each request type
  • FindContentReadRequest
  • FoundContentWriteRequest
  • OfferWriteRequest
  • AcceptReadRequest
• Separates logic / packet handlers for each request type
  • Eliminates conditionals within utp methods

3. PortalNetworkUtp

• Moves most request methods into ContentRequest classes
• PortalNetworkUtp class refactored to just manage open requests