PHP 4.0 migration guides

see DOC-9626 for Node 

For reference, these were the changes made for Node 4.0

• transactions
• client settings
• management API stuffs
• metrics and logging
• capella first
• sdk-release-notes:
• These pages cover the 4.x and 3.x versions of the Couchbase Node.js SDK.

• durability-replication-failure-considerations.adoc (Legacy durability not supported in cb++)
• client-settings
• WARNING: The backend implementation of client settings changed substantially in 4.0 and is not currently fully documented.
• This will be resolved in a future 4.x release.
• See xref:project-docs:migrating-sdk-code-to-3.n.adoc#sdk4-specifics[more details on migrating to 4.0].

• collecting-information-and-logging.adoc
• WARNING: the Logging implementation has changed substantially in 4.0 and is not currently fully documented.
• This will be resolved in a future 4.x release.
• The Node.js SDK internally uses the libcouchbase API (since 4.0 implemented by the Couchbase++ library) to perform
• operations.

• hello-world/overview
• libcouchbase mention

• start-using-sdk
• NB: need to mention Alpine Linux
• The Couchbase SDK API 3 (implemented by Node.js SDK 3.x and 4.x) is a complete rewrite of the API, reducing the number of overloads to present a simplified surface area, and adding support for Couchbase Server features like xref:concept-docs:collections.adoc[Collections and Scopes] (available from Couchbase Server 7.0).

• Renames / things to search for throughout
• libcouchbase -> Couchbase++ (with appropriate wording in context)
• SDK2 / SDK3
• SDK 2 / SDK 3
• “SDK 2 KV APIs” -> “SDK API 2 KV calls”
• SDK 3.x or 3.x
• 3.x SDK 
• 3.0 API
• the new SDK API
• 3.2 SDK -> SDK API 3.2
• .SDK 2.x vs SDK 3.x clustermanager (‘Just `clustermanager` changes)