varnishlog: if -m given, but no -c and -b, assume both

If we don't add -c and -b in there, varnishlog will print all
transactions that aren't associated with a session.  That is likely to
not be what the user wants.

Fixes: #1071
Handle Cache-control: (private|no-cache|no-store) by default

As per discussion at the Varnish dev meeting, seeing Cache-control:
no-cache (and friends) now disable caching by default.  As a twist, we
respect Surrogate-control if that is present, in the default VCL.

Fixes: 1124
References: 477