* Implement first response parts of http caching
* Implement cached response for static resources
* Implement HTTP caching for json responses
* Fix last seen value for online players
* Implement http caching for pages (.html)
* Use placeholder cache even with async requests.
Affects issues:
- Close#2813
- Customizable resources
- Snippets
- Fixed issue with a web resource being fetched on enable (favicon in ResponseResolver)
- Fixed some issues with Config#addNode used in an orElse block of Optional
- Deprecated PlanFiles#getCustomizableResourceOrDefault