add changelog

CHANGELOG

+## Centreon 2.6.2
+
+Features
+========
+Modules can extend actions after restart/reload pollers
+
+Security fixes
+==============
+#2979 : Secure the type of media file can be uploaded
+Fix some SAL injections
+
+Bug fixes
+=========
+#3559 : Fix query with MariaDB / MySQL configure in STRICT_TRANS_TABLES
+#3554 : Can send acknownlegment with multiline from monitoring page
+#3397 : Fix display graph with unicode characters in metrics name
+#2362 : Correct value when use index_data insered by Centreon Broker in configuration
+#1195 : Display correct number of pollers in status bar
+#196 : Display all colunms when filter the Monitoring services unhandled view
+
+
+
 ## Centreon 2.6.1
 
 Bug fixes