Please add pk-serialize

[plkrueger]

Please add pk-serialize which can be downloaded from https://github.com/plkrueger/pk-serialize. This implements yet another serialization package for arbitrary common-lisp objects and instances. Dumped files can be easily read and even edited if desired.

[plkrueger]

Previous comment: I forgot that there are some CCL-specific function calls in this code. Please hold off trying to add this until I resolve that.

This is now resolved. Code was tested on CCL and SBCL