draft: major refactor

[jptosso]

New features

• Amazing performance improvements:
  • New variable parsing with better performance
  • Logging improvements
  • New cache eviction system
  • New sync.Pools for often used resources
• Reload system: a HUP signal will safely reload all applications and rules, shutdown will safely finish ongoing transactions
• Advanced concurrency manager to avoid DOS
• Switched to zerolog
• Implements CRS by default
• More code coverage, the new SPOE engine is easier to test
• Now you can have multiple configuration files, for example, you can have one application per file inside a directory

TODO:

• [x] Implement Response processing
• [x] Implement contextual logging
• [x] Test configurations merging
• [x] Implement HUP and KILL signal handlers
• [x] Implement eviction policy

[jptosso]

@sts could you help us fix the e2e for this branch? I'm not sure how it works