Preparation for Overhaul

Added

• Support for custom listener services #115
• LogOut for user when connection gets closed #93
  • New interface IMembershipProviderAsync

Fixed

• S3 directory list fix #103
• Final(?) fix for #82

Changed

• Use many interfaces from ASP.NET Core 3.0
• Implicit TLS is now a core feature activated using UseImplicitTls()
• Better decoupling of server and connection