OAK-1817 - NPE in MarkSweepGarbageCollector.saveBatchToFile during Datastore GC with FileDataStore

Adding testcase to try to reproduce the issue

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1596241 13f79535-47bb-0310-9956-ffa450edef68
OAK-301: Document Oak
Move images into same directory as the markdown file so they are rendered when viewing on github. Also make sure the resource plugin copies those images when bulding the site

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1596249 13f79535-47bb-0310-9956-ffa450edef68