Patch from Raúl Wegmann from bug #56735 / GitHub Pull #10 - Rationalise POI temp file creation to the TempFile util class, and allow a system wide setting of where Temp files (eg for SXSSF) go, via TempFile / TempFileCreationStrategy

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1613246 13f79535-47bb-0310-9956-ffa450edef68