PHP docBlocks for Codex

@raamdev I spent some time going back through the `advanced-cache.tpl.php` file and the `quick-cache.inc.php` in both the lite and pro versions. I added documentation for each property/constant/method in both of these files across both versions of the plugin.

There is more work to be done for other class files... I'll just leave those file you I suppose. Anyway, I thought it might be helpful for me to at least document some of the code that I originally wrote, and also to offer you something that you can build onto in the future.

My docBlocks are not perfect, but they should serve as a good starting point for a better codex. At the very least, I think it might help you understand how the application works overall better.

This PR includes all of the new docBlocks in the source code, and an updated `/codex` for each version of the plugin that is based on these new docBlocks.