Migrate FilterType and ListSortTYpe to kotlin

db/src/main/java/com/readrops/db/filters/FilterType.kt

@@ -1,6 +1,6 @@
 package com.readrops.db.filters;
 
-public enum FilterType {
+enum class FilterType {
     FEED_FILTER,
     FOLDER_FILER,
     READ_IT_LATER_FILTER,

db/src/main/java/com/readrops/db/filters/ListSortType.java

@@ -1,6 +0,0 @@
-package com.readrops.db.filters;
-
-public enum ListSortType {
-    NEWEST_TO_OLDEST,
-    OLDEST_TO_NEWEST
-}

db/src/main/java/com/readrops/db/filters/ListSortType.kt

@@ -0,0 +1,6 @@
+package com.readrops.db.filters
+
+enum class ListSortType {
+    NEWEST_TO_OLDEST,
+    OLDEST_TO_NEWEST
+}