TODO
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Split one-big-script into a few modules.

Possibly add HTTP Proxy server so blocked access attemps can be
intercepted and the user can be chided.

Add Whitelist via the proxy server allowing access to sites based
on application level information.  For example also allow sites that
are referenced by whitelisted sites by checking the Referer information.

Better checking the state of the standard firewall chains.  Currently
the program assumes a default empty set of chains with the policy
ACCEPT.  This will likely be difficult once you get into REJECT policies
and allowing established, nat rules, and other pre-existing restrictive
rules.  However, it may not be needed at all, a user with such rules
would not need this program to simply block and unblock sites.  DUH!

Possible split lines for the script:

Server - the proxy
Root - for the root stuff
UI - for the GUI
Config - for the configuration state