Simplified varnish cookie cleanup rules

* Removed cleanup of 'has_js' (remnant of drupal stuff from vcl template)
* Removed specific cookie checks, instead removing any underscore prefixed
* Left in removal of Google Analytics "utm" prefixed cookies (debateable, @ericclemmons might have opinion here)

Fixes #28 but more vcl cleanup to do...
Simplified cookie logic in receive/wordpress.vcl

* The existing wp cookie check was *starting with* `wp-` or `wprdpress_`, but would not match a 2nd or higher position wp cookie
* The second url check for `wp-(login|admin)` was no longer necessary, so removing all cookies past that point is more efficient
Removed extra GA cookie checks (turned out to be components of __utmz, not cookies themselves)
Switch varnish from malloc to file caching backend

Fixes #53
Removed cache bypass for local.* hostname
Remove caching for static files
Pipe all requests for wp-login or wp-admin

This appears necessary for the web ui installs/updates to work. Should fix #30, and may fix #34 as well!
Probably best to still pass wp-login requests, and only pipe wp-admin reqs
Merge pull request #62 from genesis/28-varnish-vcl-cleanup

[RFC] Varnish VCL cleanup