As part of the cache purging changes added in 1e3beb6e9, we should ignore our query string so caching isn't bypassed.

Include post-password cookies in those exempt from caching, otherwise password-protected posts can end up in cache.

Fixes #6.

Rather than check the request method, check for the presence of posted data upon which some script would have to act.

Include query strings when building cache keys, to avoid corrupting caches with data WP generates based on present query strings.

See #3.

See #3.

Fixes #3.

Fixes #4.

Improve debugging messages and reduce duplication. Many of these came from the original plugin this is forked from.

See #1.

See #3.

* Cache protocol-specific pages
* Ignore all query args and hashes, not just that used to clear a page's cache

Fixes #2.

Probably needs a new name.

Improve use of global space by declaring a local variable global, rather than always using the Superglobal.

It's easier to read, especially with the use of the `$_SERVER` superglobal.

Conslidates debug messages and prevents them from corrupting XML layouts.

Revert helper function for loading WP, introduced in 25ebf3a1. It causes the brokenness noted in that commit, somehow related to calling require_once inside a function.

Currently broken (causes an error with $wpdb).

Clarify purpose of `cache` flag by renaming to `cached` as it indicates that the current page was served from cache