improve .gitignore

.gitignore

@@ -1,9 +1,18 @@
 sonar-server/src/main/webapp/stylesheets/sonar-colorizer.css
+
+# Maven
 target/
+
+# IntelliJ IDEA
 *.iws
 *.iml
 *.ipr
 
+# Eclipse
+.classpath
+.project
+.settings
+
 # ---- Mac OS X
 .DS_Store?
 Icon?
@@ -17,4 +26,4 @@ Icon?
 # Windows image file caches
 Thumbs.db 
 # Folder config file
-Desktop.ini
+Desktop.ini