JMAP Blob Management

The JSON Meta Application Protocol (JMAP) base protocol ([JMAP-CORE]) provides the ability to upload and download arbitrary binary data via HTTP POST and GET on a defined endpoint. This binary data is called a "blob". This extension adds additional ways to create and access blobs by making inline method calls within a standard JMAP request. It also adds a reverse lookup mechanism to discover where blobs are referenced within other data types, support for large blobs via chunked construction with server-side optimisation, and server-side blob conversion operations including image format conversion, archive creation and extraction, compression and decompression, and delta/ patch operations.