[AltKit] Replaces dedicated AltKit module with shared files across targets

Treating AltKit as a full module resulted in more complexity than necessary, when we really just wanted to share some files between different targets. Now we can share individual files across modules as-needed without AltKit overhead.

Shared/Connections/NetworkConnection.swift

@@ -0,0 +1,54 @@
+//
+//  NetworkConnection.swift
+//  AltKit
+//
+//  Created by Riley Testut on 6/1/20.
+//  Copyright © 2020 Riley Testut. All rights reserved.
+//
+
+import Foundation
+import Network
+
+public class NetworkConnection: NSObject, Connection
+{
+    public let nwConnection: NWConnection
+    
+    public init(_ nwConnection: NWConnection)
+    {
+        self.nwConnection = nwConnection
+    }
+    
+    public func __send(_ data: Data, completionHandler: @escaping (Bool, Error?) -> Void)
+    {
+        self.nwConnection.send(content: data, completion: .contentProcessed { (error) in
+            completionHandler(error == nil, error)
+        })
+    }
+    
+    public func __receiveData(expectedSize: Int, completionHandler: @escaping (Data?, Error?) -> Void)
+    {
+        self.nwConnection.receive(minimumIncompleteLength: expectedSize, maximumLength: expectedSize) { (data, context, isComplete, error) in
+            guard data != nil || error != nil else {
+                return completionHandler(nil, ALTServerError(.lostConnection))
+            }
+            
+            completionHandler(data, error)
+        }
+    }
+    
+    public func disconnect()
+    {
+        switch self.nwConnection.state
+        {
+        case .cancelled, .failed: break
+        default: self.nwConnection.cancel()
+        }
+    }
+}
+
+extension NetworkConnection
+{
+    override public var description: String {
+        return "\(self.nwConnection.endpoint) (Network)"
+    }
+}