Update slingstart to use txt files

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1627820 13f79535-47bb-0310-9956-ffa450edef68
Implement txt format for reading and writing

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1627821 13f79535-47bb-0310-9956-ffa450edef68