Add :no-save keyword for Org capture templates

* lisp/org-capture.el (org-capture-finalize): Do not save the target
  capture file if :no-save keyword is non-nil in the capture template.
* doc/org-manual.org (Template elements),
  lisp/org-capture.el (org-capture-templates): Document :no-save.

Ref: https://lists.gnu.org/r/emacs-orgmode/2018-09/msg00325.html

doc/org-manual.org

@@ -7352,6 +7352,10 @@ Now lets look at the elements of a template definition.  Each entry in
           If the target file was not yet visited when capture was invoked, kill
           the buffer again after capture is completed.
 
+     - ~:no-save~ ::
+
+          Do not save the target file after finishing the capture.
+
 **** Template expansion
 :PROPERTIES:
 :DESCRIPTION: Filling in information about time and context.

lisp/org-capture.el

@@ -266,6 +266,8 @@ properties are:
                      capture was invoked, kill the buffer again after capture
                      is finalized.
 
+ :no-save            Do not save the target file after finishing the capture.
+
 The template defines the text to be inserted.  Often this is an
 Org mode entry (so the first line should start with a star) that
 will be filed as a child of the target headline.  It can also be
@@ -795,8 +797,8 @@ captured item after finalizing."
 	(goto-char (org-capture-get :decrypted))
 	(org-encrypt-entry)))
 
-    ;; Kill the indirect buffer
-    (save-buffer)
+    (unless (org-capture-get :no-save) (save-buffer))
+
     (let ((return-wconf (org-capture-get :return-to-wconf 'local))
 	  (new-buffer (org-capture-get :new-buffer 'local))
 	  (kill-buffer (org-capture-get :kill-buffer 'local))