Adding ".gwt/", "gwt-unitCache/", "www-test" and ".gwt-tmp/" to .gitignore

GWT.gitignore

@@ -14,3 +14,15 @@ gwt-unitCache/
 # more caches and things from deploy #
 war/WEB-INF/deploy/
 war/WEB-INF/classes/
+
+#compilation logs
+.gwt/
+
+#caching for already compiled files
+gwt-unitCache/
+
+#gwt junit compilation files
+www-test/
+
+#old GWT (1.5) created this dir
+.gwt-tmp/