PDFBOX-2296: DRY refactoring of createFilteredStream()
PDFBOX-2262: don't lose stream contents when changing filters, as suggested by Dominic Tubach

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1621371 13f79535-47bb-0310-9956-ffa450edef68