Fix database migration of field forceOverwrite to NameCollisionPolicy

Signed-off-by: Alice Gaudon <alice@gaudon.pro>

src/main/java/com/owncloud/android/files/services/FileUploader.java

@@ -1053,10 +1053,13 @@ public class FileUploader extends Service
     }
 
 
+    /**
+     * Ordinal of enumerated constants is important for old data compatibility.
+     */
     public enum NameCollisionPolicy {
+        RENAME, // Ordinal corresponds to old forceOverwrite = false (0 in database)
+        OVERWRITE, // Ordinal corresponds to old forceOverwrite = true (1 in database)
         CANCEL,
-        RENAME,
-        OVERWRITE,
         ASK_USER;
 
         public static final NameCollisionPolicy DEFAULT = RENAME;

src/main/java/com/owncloud/android/providers/FileContentProvider.java

@@ -2147,7 +2147,7 @@ public class FileContentProvider extends ContentProvider {
                                    ProviderTableMeta.UPLOADS_STATUS + ", " +
                                    ProviderTableMeta.UPLOADS_LOCAL_BEHAVIOUR + ", " +
                                    ProviderTableMeta.UPLOADS_UPLOAD_TIME + ", " +
-                                   "force_overwrite" + ", " +
+                                   "force_overwrite" + ", " + // See FileUploader.NameCollisionPolicy
                                    ProviderTableMeta.UPLOADS_IS_CREATE_REMOTE_FOLDER + ", " +
                                    ProviderTableMeta.UPLOADS_UPLOAD_END_TIMESTAMP + ", " +
                                    ProviderTableMeta.UPLOADS_LAST_RESULT + ", " +