refactor 'create thumbnail' code in web.lisp to call from utils.

I've applied the changes to the singe and multi upload defroutes.

src/web.lisp

@@ -791,12 +791,7 @@
 		  (nera:add-storage-file file-name
 					 (utils:slugify file-name)
 					 (caddr storage-file))
-		  (utils:run-bash-command
-		   (format nil "convert ~a -resize 512x512\\> ~a"
-			   (storage:file-exists-p "" "media" (utils:slugify file-name))
-			   (storage:make-path "" "media"
-					      (format nil "thumbnail-~a"
-						      (utils:slugify file-name)))))
+		  (utils:create-thumbnail (utils:slugify file-name))
 		  (utils:set-alert "File uploaded.")
 		  (redirect "/storage/manage")))
 	 ;; Not Authorised
@@ -828,7 +823,8 @@
 		     (utils:slugify (caddr item)) (cdr item))
 		    (nera:add-storage-file (caddr item)
 					   (utils:slugify (caddr item))
-					   (cadddr item)))
+					   (cadddr item))		     
+		    (utils:create-thumbnail (utils:slugify (caddr item))))
 		     (utils:set-alert "Multi-File upload complete.")
 		     (redirect "/storage/manage")))
 	    ;; Not Authorised