"none" header avoids result post-process

This patch introduces a new header argument which hide all code block
results from Emacs so that they are not processed into Emacs-lisp
objects; a process which may take a great deal of time for large
objects.

* lisp/ob.el (org-babel-common-header-args-w-values): Adding the new
  "none" header argument.
  (org-babel-execute-src-block): Don't do *any* result processing if the
  "none" header argument has been specified.
  (org-babel-sha1-hash): Remove the none header argument from
  header arg lists when calculating cache sums.
  (org-babel-insert-result): Flesh out some documentation.

lisp/ob.el

@@ -421,7 +421,7 @@ then run `org-babel-pop-to-session'."
     (padline	. ((yes no)))
     (results	. ((file list vector table scalar verbatim)
 		   (raw html latex org code pp drawer)
-		   (replace silent append prepend)
+		   (replace silent none append prepend)
 		   (output value)))
     (rownames	. ((no yes)))
     (sep	. :any)
@@ -562,6 +562,8 @@ block."
 		(message "executing %s code block%s..."
 			 (capitalize lang)
 			 (if (nth 4 info) (format " (%s)" (nth 4 info)) ""))
+		(if (member "none" result-params)
+		(message "result silenced")
 		(setq result
 		      ((lambda (result)
 			 (if (and (eq (cdr (assoc :result-type params)) 'value)
@@ -581,7 +583,8 @@ block."
 		(org-babel-insert-result
 		 result result-params info new-hash indent lang)
 		(run-hooks 'org-babel-after-execute-hook)
-		result))
+		result
+		)))
 	  (setq call-process-region 'org-babel-call-process-region-original))))))
 
 (defun org-babel-expand-body:generic (body params &optional var-lines)
@@ -1028,7 +1031,8 @@ the current subtree."
 	  (sort (copy-sequence (nth 2 info))
 		(lambda (a b) (string< (car a) (car b)))))
     (let* ((rm (lambda (lst)
-		 (dolist (p '("replace" "silent" "append" "prepend"))
+		 (dolist (p '("replace" "silent" "none"
+			      "append" "prepend"))
 		   (setq lst (remove p lst)))
 		 lst))
 	   (norm (lambda (arg)
@@ -1851,7 +1855,10 @@ RESULT-PARAMS can take the following values:
 replace - (default option) insert results after the source block
           replacing any previously inserted results
 
-silent -- no results are inserted
+silent -- no results are inserted into the Org-mode buffer but
+          the results are echoed to the minibuffer and are
+          ingested by Emacs (a potentially time consuming
+          process)
 
 file ---- the results are interpreted as a file path, and are
           inserted into the buffer using the Org-mode file syntax