added mvn_cheat-sheet.txt with some useful+common maven commands; should be part of site once we've completely switched to Maven

JSPWIKI-771: 
  - added apache rat report configuration 
  - added AL to root build.xml

git-svn-id: https://svn.apache.org/repos/asf/incubator/jspwiki/branches/MVN3_BRANCH@1469995 13f79535-47bb-0310-9956-ffa450edef68