command line tools for package upgrade problem descriptions

 A CUDF document describe an upgrade problem, as faced by package
 managers in popular package-based GNU/Linux distributions.
 .
 A CUDF document consists of a package universe and of a user request.
 The package universe describes all packages known to the package
 manager, a subset of which (the package status) denotes the package
 being currently installed on the target machine. The user request
 denotes a change to the package status as requested by the user.
 .
 A CUDF document is naturally complemented by a solution describing
 the resulting package status (if any) implementing the user request,
 as found by a package manager.
 .
 This package contains command line tools to manipulate CUDF and
 related documents. In particular it contains cudf-check, which
 enables checking of document properties such as installation
 consistency and matching of problems with their solutions.