(#21427) Respect Accept header for save

The REST save action will now respect the formats that are requested in
the Accept header. In order to retain backwards compatibility for
clients that have never been required to specify an Accept before this
it will also default to :yaml when no Accept is provided. If an Accept
is provided but none of the wanted formats are suitable an error is
raised, just like find and search.

In order to report the status of an unkown Accept header correctly this
also adds the capability of raising web related exceptions that contain
the HTTP response code that needs to be used.