Pull request to update openshift-tomcat-quickstart from Tomcat 7.0.29 to 7.0.42

Hi, following the instructions I added in the "HowToUpdate.md" file below, I've updated the Tomcat embedded in this quickstart to 7.0.42 and also fattened up the README.md for users.  I've tested it following the usual instructions in the README.md and got it to work without a problem (http://tomcat742-gmazza.rhcloud.com/, also with a sample application at http://tomcat742-gmazza.rhcloud.com/JSPWiki/).