Config documentation updates

I have committed updates to the cf_gen tool which fix some of the
annoyances I've had with the configuration file template syntax.

We can now pre-define multiple lines of default config and provide a
textual alternative representation to hide the internal config
definition from the distributed documentation.

Amos

-- 
Please be using
   Current Stable Squid 2.7.STABLE9 or 3.1.14
   Beta testers wanted for 3.2.0.10