Use a7zip to extract archives

app/src/main/java/com/hippo/ehviewer/EhApplication.java

@@ -31,6 +31,7 @@ import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.support.v4.util.LruCache;
 import android.util.Log;
+import com.hippo.a7zip.A7Zip;
 import com.hippo.beerbelly.SimpleDiskCache;
 import com.hippo.conaco.Conaco;
 import com.hippo.content.RecordingApplication;
@@ -104,6 +105,7 @@ public class EhApplication extends RecordingApplication {
         EhEngine.initialize();
         BitmapUtils.initialize(this);
         Image.initialize(this);
+        A7Zip.initialize(this);
 
         if (EhDB.needMerge()) {
             EhDB.mergeOldDB(this);