ServerMultiplex: Introduces a server mutiplexer

- Also moves all the existing Wemo* stuff over to support the multiplexer
- Moves MainViewController to be the owner of the multiplexer, and its delegate

XIONControlPanel/Controllers/SwitchesViewController.swift

@@ -12,12 +12,7 @@ import UIKit
 
 protocol SwitchesViewControllerDelegate: class
 {
-    func switchesViewControllerDidToggleDevices(_ controller: SwitchesViewController, devices: [WemoDevice])
-}
-
-extension SwitchesViewControllerDelegate
-{
-    func switchesViewControllerDidToggleDevices(_ controller: SwitchesViewController, devices: [WemoDevice]) {}
+    func switchesViewControllerDidToggleDevices(_ controller: SwitchesViewController, devices: [AnyDevice])
 }
 
 class SwitchesViewController: UIViewController,
@@ -117,12 +112,12 @@ class SwitchesViewController: UIViewController,
     
     // MARK: API
     
-    var devices: [WemoDevice] = []
+    var devices: [AnyDevice] = []
     {
         didSet
         {
             // sort devices by name
-            self.devices.sort(by: { (d1: WemoDevice, d2: WemoDevice) -> Bool in
+            self.devices.sort(by: { (d1: Device, d2: Device) -> Bool in
                 return (d1.name.compare(d2.name, options: .caseInsensitive, range: nil, locale: nil) == .orderedAscending)
             })
             
@@ -132,6 +127,19 @@ class SwitchesViewController: UIViewController,
         }
     }
     
+    public func devicesStateChanged(_ changedDevices: [AnyDevice])
+    {
+        var snapshot = _collectionViewDataSource.snapshot()
+        changedDevices.forEach { changedDevice in
+            if let existingDevice = (self.devices.first { $0.hashValue == changedDevice.hashValue }) {
+                existingDevice.state = changedDevice.state
+                snapshot.reloadItems([ existingDevice.hashValue ])
+            }
+        }
+        
+        _collectionViewDataSource.apply(snapshot, animatingDifferences: true)
+    }
+    
     // MARK: UICollectionView
     
     func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath, identifier: Int) -> UICollectionViewCell?