Hackage/List.hs: port showPackageInfo to pretty-printing combinators, improve display of packages with multi-line synopses

There were two issues;
  * Unpacking links that point to files not yet unpacked
  * Used the link target as absolute path, but it's relative
This patch addresses both issues, which is ticket #246.
There may still be errors if a link refer to another link which has not
been unpacked yet.

Depend on latest Cabal lib version and bump our own version due to recent
feature additions and removal of the 'info' command.

Add completion of packages to the commands install, list, upgrade and fetch.
Only complete packages if the user is not trying to complete a flag.
Complete with package-versions if the package name ends with a dash,
otherwise just complete with the package names.

"cabal configure --global" was incorrectly passing the user prefix to setup.

Previously we took the available packages and did an inner join with the
installed packages so we missed out packages like base which are installed
by not available. Now we get the selected installed and available package
sets and do a full outer join using a sort and merge operation.
Also use a proper data type to hold the info we print about each package.

Provides a output format that is easier to pass on to unix tools and other
scripting tools. Also works together with --installed.

Adding --installed to 'cabal list' will make it print only packages that are
installed.

Make the output of 'cabal list' prettier. 
$ cabal list xmonad
 * xmonad
      Latest version available: 0.6
      Latest installed version: 0.6
      Homepage: http://xmonad.org
      Category: System
      Synopsis: A tiling window manager
      License:  BSD3
 * xmonad-contrib ...[snip]
Very much like the gentoo tools eix and esearch.
This targets part of ticket #235. It still does not show packages that are
installed but not available.

In -v mode info produced a detailed tree explaining the dependency
resolution. That feature has been moved into 'install --dry-run -v'.

Also adjust the default for --dry-run to be false rather than empty.

and give more detailed error messages for internal error conditions.
Fixes a problem where installing a set of packages where several depended
on the same package would give us a ResolvedDependency list containing
multiple copies of that package. The DepGraph was expecting unique packages.
Resolving package deps and generating install plans needs more thought
and better specified invariants.

Added readBinaryFile for on use (uploading .tar.gz files)
Remove readURI as it was not being used.

And note problem #246 about unpacking tar files with links

Several of the general util functions in Hackage.Utils are now in the main
Cabal lib in Distribution.Simple.Utils so we use those.
The Package class moved into Distribution.Package.
Use the packageId class function in more places.

and instead of exitWith ExitSuccess just return through main rather than
throwing an exception

A naive implementation of 'cabal check'.
It will list the errors and warnings as implemented by Cabal, yielding them
in groups of severity. Currently ignores verbosity levels, no additional
arguments are understood. This addresses ticket #211.

Then print out at the end why packages failed. This is a step closer to
producing detailed build reports.

And use that to simplify the code slightly. Also add an assertion into
removeFailed, that the first returned result is the failed package itself,
since we'll rely on this in the install code.

and adapt to the minor finalisePackageDescription change

This allows us to figure out what to do when installing a single package
fails. Instead of just carrying on as if nothing had happened and then
failing several other packages which depended on the one that failed
initially we can cut those dependent packages out as soon as the first one
fails and if there is anything left that did not depend on the failed
package then we can try and carry on.

The InstalledPackageIndex replaces our Hackage.LocalIndex module

Due to recent Cabal api changes

Just like the install command has always done. This makes them consistent.
So by default that means cabal configure uses --user --prefix=$HOME/.cabal