remove unrelated DataFormat code (not worried about wrap-around here since Excel supports up to 250 data formats and we're using the short data type)
replace complex write-out, close, read-back, delete code with new better test apparatus
git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1721922 13f79535-47bb-0310-9956-ffa450edef68