TODO:
	write more automated test-cases
	allow to specify a keyring to use.
	allow to specify which keys are accepted for include and includedsc.
	add override-support while updating (or decide if this should be done)
	extend FilterFormula, FilterList et al to specify type/architecture/component
	switch to only include if source is present
	action to redownload missing pool/ files from some update-rules (looking for md5sum)
	check for harmful override entries (Package, Source, ....)

half far goals:
	rewrite error handling, caching error messages and handling Ctrl-C better.

far goals:
	check for source of package, 
	      for sources without packages.
	      for unmeet Dependencies
	      for unmeet Build-dependencies.
	switch to only include a package if no binaries from an older
		source of this package would be left.
	write dokumentation, some examples
	allow multiple versions in a distribution (needs major rewrite I fear)
	option to keep source to each binary (needs mutliple source versions)
