Add formulas

[siriusnottin]

Description

Add support for formulas.

Based on the SpinupWP API documentation.

List of formulas to add:

• Get Server details
• Get Site details
• Get Event details

List of action formulas to add:

Server

• Provision a new server
• Delete a server
• Reboot a server
• Restart:
  • Nginx service
  • PHP-FPM service
  • MySQL service

Site

• Create a site
• Delete a site
• Purge page cache
• Purge object cache
• Correct file permissions
• Run a git deployment