Adds LoggedError Core Data entity

Allows us to save certain errors to disk so that they can be viewed again later from an error log.

AltStoreCore/Model/StoreApp.swift

@@ -59,6 +59,8 @@ public class StoreApp: NSManagedObject, Decodable, Fetchable
     @NSManaged @objc(source) public var _source: Source?
     @NSManaged @objc(permissions) public var _permissions: NSOrderedSet
     
+    @NSManaged public private(set) var loggedErrors: NSSet /* Set<LoggedError> */ // Use NSSet to avoid eagerly fetching values.
+    
     @nonobjc public var source: Source? {
         set {
             self._source = newValue