[umbrella] Add support for WordPress

[SergeyKleyman]

• [x] #826
• [x] #827
• [ ] #812
• [ ] #816
• [ ] Automatically discover service name
• [ ] #905
• [ ] Automatically name a transaction based the selected route
• [ ] Capture errors escaping from the application to the framework
• [x] It seems that WordPress uses mysqli (AKA MySQL Improved Extension) for database queries so #639 - Add support mysqli (AKA MySQL Improved Extension) might a prerequisite.
• [ ] Automated tests
  • [ ] PHP workers process daemon + front-end server combinations to cover:
    • [ ] PHP-FPM + NGINX
    • [ ] mod_php + Apache
  • [ ] With/out OpCache enabled
  • [ ] In addition to basic WordPress setup we should test with the following plugins to
    • [ ] #814

[archon810]

Yes please. We'll be the first to give it a go once it's stable.

[ramon-yoast]

@SergeyKleyman could you elaborate why the milestones have been bumped twice from 8.3 to 8.5?