[MERGE] Developer doc: container format

[Harald Meland]

[Andrew Bennetts]

> Hi all,
>
> This document adds a description of a basic container format to
> doc/developers.  This was worked out with Robert on Friday.

The format appears to try being somewhat human readable, by specifying
that newlines must be used in key positions.  So, maybe it would be a
good idea to explicitly specify whether the length of a full-text
record includes a final newline or not, and maybe even require an
explicit newline to be included after the content.
-- 
Harald