Implement New VHM Features and Update VCL

This update does the following:

- Fixup string concat for varnish_version 3.
- Add zope2_vhm_port to be able to explicitly define a response
  port in VHM URLs.
- Add zope2_vhm_ssl to use VHM to render https urls.
- Add zope2_vhm_ssl_port to be able to explicitly define a response
  port in VHM URLs for ssl.
- Update verbose-headers to use upstream debug example:
  https://www.varnish-cache.org/trac/wiki/VCLExampleHitMissHeader
- Add cookie-fixup to better support caching of plone conent
  and to ensure no authenticated content gets cached.
  http://developer.plone.org/hosting/varnish.html
- Update VCL templates to be more flexible.

I've tested most configuration combinations with both varnish 2 and varnish 3.