firmware-download/unpack-script:
 * add support for beta/labor firmwares located in ftp://ftp.avm.de/fritz.box/beta
 * download only files matching *.image pattern (reduces amount of data downloaded)
 * fix various unpacking bugs


git-svn-id: file:///var/svn/freetz/trunk@11189 149334a1-2f27-0410-a3b9-fc62619ac1e6