Allow packages to use of lzma for compression

The Ubuntu alternate cd is running low on space as always and LZMA can compress much tighter than gzip or bzip2. So we intend to allow packages to use LZMA compression as an alternative to gzip and bzip2. Switching to lzma could save us up to 175MB on the alternate cd over what we are currently saving with using gzip, and bzip2 depending on which and how many packages we convert.

If we also start using lzma for Packages files we could save ~ 70K for main and ~ 430K for the universe Packages file. That might not sound like much but adds up since it is downloaded frequently.

Launchpad will need to be modified to support lzma uploads and to check that the needed predepends listed in the package.