Add a Acquire::CompressionTypes config variable from there the

Add a Acquire::CompressionTypes config variable from there the
acquire-items choose which compression file they should (try first to)
download to easily add new or change the order of the compression types.
And because it is easy now we directly add builtin lzma support.

The compression ratio is better than bzip2 but we prefer the later for now
as no (official) mirror uses lzma, so this would only generate useless
hits on the servers. Maybe sometime in the future lzma will be the default...

[apt-pkg/acquire-item.cc]
- use configsettings for dynamic compression type use and order.
  Based on a patch by Jyrki Muukkonen, thanks! (LP: #71746)
[apt-pkg/init.cc]
- add default configuration for compression types and add lzma
  support. Order is now bzip2, lzma, gzip, none (Closes: #510526)
[ftparchive/writer.cc]
- add lzma support also here, patch for this (and inspiration for
  the one above) by Robert Millan, thanks!