Fetch client code based on info in a client-info file.

This makes it possible to bootstrap with a specific version of the
client code. The idea is that if future versions of the client become
incompatible with your project development environment, you can still
use a version that works.

Remove special-casing of asdf.lisp from the bootstrap process; it will
now be provided in quicklisp.tar.
Remove unnecessary *DEFAULT-PATHNAME-DEFAULTS* canonicalization.
Updates for specifying dist info during install.
Add ASDF URL stuff to client info and initial setup.
Save client-info.sexp during bootstrap.
Adapt to new client-info.sexp structure.
New user-agent version.
Remove asdf.lisp and setup.lisp. They're in quicklisp-client now.
Update copyright info in LICENSE.txt.
Make version URLs from a hostname variable.
Update version to 2014-01-28.