* PCBC-443: Remove PCS dependency and rewrite PHP stubs using Zend C API
* PCBC-382: Implement cluster-level authorization using ClassicAuthenticator
* Migrate API to \Couchbase namespace (old API still available on toplevel as aliases,
* PCBC-383: Cross-bucket joins for N1QL (see examples/api/couchbase.N1qlQuery.crossBucket.php)
* Refresh API documentation, describe all input options, put everything into single file
(see api/*.php), and prepare them for PHPStorm (https://github.com/JetBrains/phpstorm-stubs/pull/180)
* PCBC-386: Implement Datastructures API: List, Set, Map and Queue (see tests/DatastructuresTest.php)
* Improve connection management, persistent connections by default, track and close idle connections.