teach git to ignore .DS_STORE files

.gitignore

@@ -8,28 +8,32 @@ release.properties
 dependency-reduced-pom.xml
 buildNumber.properties
 .mvn/timing.properties
+
 ### Java template
 *.class
 
-# Mobile Tools for Java (J2ME)
+### Mobile Tools for Java (J2ME)
 .mtj.tmp/
 
-# Package Files #
+### Package Files #
 *.jar
 *.war
 *.ear
 
-# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+### virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
 hs_err_pid*
 
-# logs files
+### logs files
 *.log
 
-# Certs
+### Certs
 *.jks
 *.cer
 *.pem
 
-# IDE files
+### IDE files
 .idea/
 *.iml
+
+#File System specific files
+.DS_STORE