Replace some "write" permissions with with "read" ones.

Notes for backup related classes.

src/org/thoughtcrime/securesms/RegistrationActivity.java

@@ -268,7 +268,7 @@ public class RegistrationActivity extends BaseActionBarActivity implements Verif
 
   @SuppressLint("StaticFieldLeak")
   private void initializeBackupDetection() {
-    if (!Permissions.hasAll(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
+    if (!Permissions.hasAll(this, Manifest.permission.READ_EXTERNAL_STORAGE)) {
       Log.i(TAG, "Skipping backup detection. We don't have the permission.");
       return;
     }

src/org/thoughtcrime/securesms/components/AttachmentTypeSelector.java

@@ -110,7 +110,7 @@ public class AttachmentTypeSelector extends PopupWindow {
   public void show(@NonNull Activity activity, final @NonNull View anchor) {
     updateHeight();
 
-    if (Permissions.hasAll(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
+    if (Permissions.hasAll(activity, Manifest.permission.READ_EXTERNAL_STORAGE)) {
       recentRail.setVisibility(View.VISIBLE);
       loaderManager.restartLoader(1, null, recentRail);
     } else {

src/org/thoughtcrime/securesms/jobs/LocalBackupJob.java

@@ -26,6 +26,7 @@ import java.util.Locale;
 
 import network.loki.messenger.R;
 
+//TODO AC: Needs to be refactored to use Storage Access Framework or Media Store API.
 public class LocalBackupJob extends BaseJob {
 
   public static final String KEY = "LocalBackupJob";

src/org/thoughtcrime/securesms/util/BackupUtil.java

@@ -16,6 +16,7 @@ import java.util.Arrays;
 import java.util.Calendar;
 import java.util.Locale;
 
+//TODO AC: Needs to be refactored to use Storage Access Framework or Media Store API.
 public class BackupUtil {
 
   private static final String TAG = BackupUtil.class.getSimpleName();