xF1 Add-on [bd] Cache 1.2.3

[FEATURES]
1. "Cache Pages" (guests only) for top speed
2. Admin can purge cache for individual page any time
3. "CSS to file" for faster serving, make it possible to put stylesheets behind CDN
4. “Defer JS” to make sure the page display in user browser as soon as possible.

[SUPPORTED PAGES]

• Built-in:
  • Forum List
  • Member List
  • Member View
  • Thread View (older pages only: if a thread has 10 pages, only the first 9 pages will be cached)
• XenForo Resource Manager
  • Author List
  • Author View
  • Category View
  • Resource List
  • Resource View
  • Resource History
  • Resource Reviews
  • Resource Updates
  • Update View
• XenPorta
  • Portal Page
  • Articles Page

[INSTALLATION]
1. Upload files and directories inside `upload` to XenForo's root directory. Select "Merge" for everything if you are asked
2. Import the .xml file using XenForo add-on importer
3. ???
4. Profit

[TECHNICAL INFORMATION]
"Cache Pages" keeps a copy of the whole page so it will save database queries and server resource. It is possible to render page with 0 database query, page time is cut by half in all cases (usually more, up to two third of the actual render time). The feature works with or without a cache backend, it will store data in internal data directory if no cache backend is configured.

"CSS to file" simply copies the result of css.php and put it into a static file in external data directory. Normally, a request to css.php will ask for some combination of CSS templates (not just one), the add-on hashes the requested templates and keep a copy for each combination. That sounds like a lot of wasted space but in practice there are usually less than 30 combinations in used. With this feature enabled, you can setup to serve these stylesheets with a CDN and improve speed further.