Define interfaces with only getters for the updates

This also changes the code to use the new interfaces wherever the
update is not supposed to change.

src/org/lineageos/updater/model/UpdateInfo.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2017 The LineageOS Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.lineageos.updater.model;
+
+import java.io.File;
+
+public interface UpdateInfo extends UpdateBaseInfo {
+    UpdateStatus getStatus();
+
+    int getPersistentStatus();
+
+    File getFile();
+
+    long getFileSize();
+
+    int getProgress();
+
+    long getEta();
+
+    long getSpeed();
+
+    int getInstallProgress();
+
+    boolean getAvailableOnline();
+}