Add a cache-munging script-generating script

Add a cache-munging script-generating script

Quickly pulled together a script to munge the CSS and JavaScript
for a given skin so that upgrades don't result in painful mismatches.

Warning: this Perl script generates a shell script which you must
then execute. It's not elegant in any way, it's based on the shell
commands that I issued by hand in a hurry. However, it does give
you the opportunity to examine what the script is going to do before
it munges your skin(s).

Signed-off-by: Dan Scott <dscott@laurentian.ca>