Release channel support (#239)

* Release channel support

- Show SideStore in Browse if it's not from the current SideStore source
- Change SideStore source URL and source ID based on if beta and nightly are in the version string
- Use StoreApp name for InstalledApp name to allow for source-specified name to show up in My Apps

* My Apps: Fix incorrect app name on first launch

* News: fix duplicate news items from multiple SideStore release channel sources

* Trusted Sources: Add stable and beta

AltStoreCore/Model/NewsItem.swift

@@ -32,6 +32,15 @@ public class NewsItem: NSManagedObject, Decodable, Fetchable
     @NSManaged public var storeApp: StoreApp?
     @NSManaged public var source: Source?
     
+    @objc public var isDuplicate: Bool {
+        if self.source == nil { return false }
+        
+        // Hide news from sources that begin with the SideStore identifier, and aren't from the same source as the current SideStore source
+        if self.source!.identifier.starts(with: Bundle.Info.appbundleIdentifier) && self.source!.identifier != Source.altStoreIdentifier { return true }
+        
+        return false
+    }
+    
     private enum CodingKeys: String, CodingKey
     {
         case identifier
@@ -86,6 +95,9 @@ public extension NewsItem
 {
     @nonobjc class func fetchRequest() -> NSFetchRequest<NewsItem>
     {
-        return NSFetchRequest<NewsItem>(entityName: "NewsItem")
+        let fetchRequest = NSFetchRequest<NewsItem>(entityName: "NewsItem")
+        fetchRequest.predicate = NSPredicate(format: "%K == NO",
+                                             #keyPath(NewsItem.isDuplicate))
+        return fetchRequest
     }
 }