Improve detection for logged-in users and correct order of operations to ensure logged-in users aren't shown cached pages.
Move configuration into a global and update all references. Makes for clearer separation of user options versus plugin code.
Move cache life to global space as an override, simplify how values are set.
Update companion plugin to use global settings introduced in aa697f901 and 0a647e330, simplifying administration, ensuring consistency in settings used, reducing UI clutter.
Support custom exception handler in configuration block of plugin
Update plugin name in UI
Remove extra spaces
Namespace all functions
PHPDoc and some simplification of the URL cleaner
Move Redis connection to its own function, for clarity.
Clarify purpose of `cache` flag by renaming to `cached` as it indicates that the current page was served from cache
Placeholder for future cache variants
Correct bug introduced in 35d01c958 that resulted in caches being set but never shown to the user
Further simplification of the logic used to build and display caches.

Currently broken (causes an error with $wpdb).
Revert helper function for loading WP, introduced in 25ebf3a1d. It causes the brokenness noted in that commit, somehow related to calling require_once inside a function.
Remove `require_once` calls no longer needed because logic is simplified.
Don't automatically output debugging messages, rather storing for output at the end of the page.

Conslidates debug messages and prevents them from corrupting XML layouts.
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.
Since admin requests aren't routed through the cache frontend, the global variable isn't available. Use defines for these overrides instead.

Unfortunately does mean that settings are split, but alternatives weren't appealing:
* store settings into an option via the front-end proxy (front-end writes are bad)
* store in Redis (could lose the option, randomly revealing a UI)
* pass all wp-admin requests through the proxy with early bailing to avoid breakage seems overly complicated and fragile/prone to bugs.
Correct syntax error introduced in 999f7c41d