Bug 708174 - Improve the original search dialog patch.

Fix various bugs, improve code design and efficiency, change feature
name, update the feature up to our standards (now uses GIMP preferences,
session management, less overwhelming settings...).
Also now action history is tightly tied to GimpAction and logs all
action activation (however it activates, and the show_unavailable
parameter also applies to history).
Search algorithm greatly improved with basic tokenization, better
ordering, filtering, etc.

app/actions/help-actions.c

@@ -47,7 +47,13 @@ static const GimpActionEntry help_actions[] =
     NC_("help-action", "_Context Help"), "<shift>F1",
     NC_("help-action", "Show the help for a specific user interface item"),
     G_CALLBACK (help_context_help_cmd_callback),
-    GIMP_HELP_HELP_CONTEXT }
+    GIMP_HELP_HELP_CONTEXT },
+
+  { "help-action-search", GTK_STOCK_FIND,
+    NC_("help-action", "_Search and Run a Command"), "slash",
+    NC_("help-action", "Search commands by keyword, and run them"),
+    G_CALLBACK (help_search_actions_cmd_callback),
+    GIMP_HELP_ACTION_SEARCH_DIALOG }
 };