• Set up a beta feature to allow users to test PHP 7 T213934

[x ] Assist the performance team in the setup of a sampling/profiling pipeline

• Set up curl connection pooling mechanism T210717
• Optimize deployments for PHP7
  • Allow scap to invalidate the opcode cache T211964
  • [stretch] Allow fetching the database configuration from etcd instead of files in order to reduce the cache resets T197126
• Set up A/B testing mechanism for PHP7, ramp up traffic to 20% of users