* Progress towards deleting Sockets.Abstractions
- Moved our custom DefaultConnectionContext to Sockets.Http and renamed it to HttpConnectionContext.
- Renamed ConnectionManager to HttpConnectionManager
- Use DefaultConnection in tests and benchmarks
- Delete ConnectionMetadata
* Re-layer the .NET Client into Http and non-Http
- Moved IConnection to Sockets.Abstractions and removed
HttpConnection and TransportType dependency.
- Renamed Sockets.Client to Sockets.Client.Http
- Renamed Sockets.Common to Sockets.Common.Http
- Renamed Connection to HttpConnection
- Removed HTTP dependency from HubConnection
- Removed tests that were testing connection logic in HubConnection
#518