65206 - Migrate ant / maven to gradle build
compile / jar / test of mrJars
don't include ants build.xml anymore
rename directories to match project and maven artifact names
refactor artifacts - so each project has one artifact
replace static references in hssf/dev tests with junit5 constructs, which had problems in parallel tests
increase gradle heap to 4gb because of OOM - maybe less would also work

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1888488 13f79535-47bb-0310-9956-ffa450edef68