Implement close() where necessary so resources are closed. Add close()
to tests and run existing unit tests also against the Extractor that is
built via the Factory. Also add a small test-suite to quickly execute
all extractor-related tests.
git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1493669 13f79535-47bb-0310-9956-ffa450edef68