Basic implementation of a
GadgetBlacklist, reading blacklist data
from a text file.
A single URL on a line blacklists this exact URL (case-insensitively).
A regular expression prefixed by "REGEXP" and a space on a line blacklists
all URL's that (case-insensitively) match that pattern. The regular
expression syntax is PCRE-based (using java.util.regex, so there are a few
insignificant differences). Regular expressions should be used sparingly as
they influence performance of every single gadget being rendered.
Lines starting with a "#" are comments.
# Block the illegal bar.xml gadget
# Block all gadgets from the baz.com domain (including subdomains)