Rename config file to be sample and add previous one to gitignore

Author: Igloczek

.gitignore

@@ -25,6 +25,7 @@ atlassian*
 /.grunt
 /Gruntfile.js
 /package.json
+/dev/tools/grunt/configs/themes.js
 
 /pub/media/*.*
 !/pub/media/.htaccess