Bump backup format version

app/src/main/java/com/todoroo/astrid/backup/TasksXmlExporter.java

@@ -74,8 +74,7 @@ public class TasksXmlExporter {
     private UserActivityDao userActivityDao;
     private final Preferences preferences;
 
-    // 3 is started on Version 4.6.10
+    private static final int FORMAT = 4;
-    private static final int FORMAT = 3;
     private Context context;
     private int exportCount = 0;
     private XmlSerializer xml;

app/src/main/java/com/todoroo/astrid/backup/TasksXmlImporter.java

@@ -121,7 +121,7 @@ public class TasksXmlImporter {
                         String format = xpp.getAttributeValue(null, BackupConstants.ASTRID_ATTR_FORMAT);
                         if(TextUtils.equals(format, FORMAT2)) {
                             new Format2TaskImporter(xpp);
-                        } else if(TextUtils.equals(format, FORMAT3)) {
+                        } else if(TextUtils.equals(format, FORMAT3) || TextUtils.equals(format, FORMAT4)) {
                             new Format3TaskImporter(xpp);
                         } else {
                             throw new UnsupportedOperationException(
@@ -376,6 +376,7 @@ public class TasksXmlImporter {
     // =============================================================== FORMAT3
 
     private static final String FORMAT3 = "3"; //$NON-NLS-1$
+    private static final String FORMAT4 = "4"; //$NON-NLS-1$
     private class Format3TaskImporter extends Format2TaskImporter {
 
         public Format3TaskImporter(XmlPullParser xpp) throws XmlPullParserException, IOException {