LUDOC-296 protocol: Rearrange presentation to be more top-down

LUDOC-296 protocol: Rearrange presentation to be more top-down

[2015-07-13]
Consistently use the file name 'struc_<bla>.txt' for content that
just has a structure and its description. Consistently refer to those
piece of content with the cross-reference label 'struct-<bla>'.

Mark each litteral text section(bounded by '----') with the
'[source,c]' tag so the HTML gets syntax highlighting.

[2015-07-12]
Flesh out some more of the rearrangement. Especially, try to push the
introduction of structuress to the place in the RPCs discussion where
it first occurs.

Signed-off-by: Andrew C. Uselton <andrew.c.uselton@intel.com>
Change-Id: I1c482c84d993d0793c8daeb1fca57396d3701abd
Reviewed-on: http://review.whamcloud.com/15575
Tested-by: Jenkins