Upsert documents instead of adding per default in the indexing phase

Change-Id: Ia7fccd59ce1b6a114c8e59da69f3d132a56bc7d2
diff --git a/Changes b/Changes
index b7d9b32..b0aab67 100644
--- a/Changes
+++ b/Changes
@@ -1,4 +1,4 @@
-0.58.5 2019-03-04
+0.58.5 2019-03-06
     - [bugfix] Fix bug where duplicate keys occured in
       field data output (diewald)
     - [bugfix] Fix bug where fields already set where lifted
@@ -8,6 +8,9 @@
       by adding indexCreationDate and indexLastModified field
       (diewald)
     - [bugfix] Fixed #50 multiple timeout warnings (margaretha) 
+    - [feature] Instead of adding, the Indexer now upserts documents
+      to avoid multiple documents with the same text sigle
+      (diewald)
 
 0.58.4 2019-02-05
     - [cleanup] Remove deprecated methods setLicense/getLicense,