see #8570, #7406 - I/O refactorization:
 - Move different file copy functions to Utils.copyFile (to be replaced later by Files.copy when switching to Java 7)
 - Replace all Utils.close(XXX) by Utils.close(Closeable) -> impacted plugins: commandline, mirrored_download, opendata, piclayer
 - Add new Utils.close(ZipFile)
 - Use of Utils.close almost everywhere
 - Javadoc fixes

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5874 0c6e7542-c601-0410-84e7-c038aed88b3b