app, libgimp*, plug-ins, icons: revert icon names into freedesktop...

... standard icon names and GTK+ icon names as second choice.
We should only use GIMP specific icon names as last resort, when there
is no standard or GTK+ names dedicated to the function.
This is made possible thanks to commit 3cc77b0.

s/gimp-document-recent/document-open-recent/
s/gimp-indent/format-indent-more/
s/gimp-next/go-next/
s/gimp-previous/go-previous/
s/gimp-save/document-save/
s/gimp-save-as/document-save-as/
s/gimp-revert/document-revert/
s/gimp-open/document-open/
s/gimp-document-recent/document-open-recent/
s/gimp-quit/window-close/ ou s/gimp-quit/application-exit/
s/gimp-warning/dialog-warning/
s/gimp-edit-clear/edit-clear/

s/gimp-justify-.*/gtk-justify-.*/
s/gimp-font/gtk-select-font/
s/gimp-color-palette/gtk-select-color/
s/gimp-cancel/gtk-cancel/

app/actions/documents-actions.c

@@ -38,11 +38,11 @@
 
 static const GimpActionEntry documents_actions[] =
 {
-  { "documents-popup", GIMP_STOCK_DOCUMENT_RECENT,
+  { "documents-popup", "document-open-recent",
     NC_("documents-action", "Documents Menu"), NULL, NULL, NULL,
     GIMP_HELP_DOCUMENT_DIALOG },
 
-  { "documents-open", GIMP_STOCK_OPEN,
+  { "documents-open", "document-open",
     NC_("documents-action", "_Open Image"), NULL,
     NC_("documents-action", "Open the selected entry"),
     G_CALLBACK (documents_open_cmd_callback),
@@ -60,7 +60,7 @@ static const GimpActionEntry documents_actions[] =
     G_CALLBACK (documents_file_open_dialog_cmd_callback),
     GIMP_HELP_DOCUMENT_OPEN },
 
-  { "documents-copy-location", GIMP_STOCK_CLIPBOARD,
+  { "documents-copy-location", "edit-copy",
     NC_("documents-action", "Copy Image _Location"), NULL,
     NC_("documents-action", "Copy image location to clipboard"),
     G_CALLBACK (documents_copy_location_cmd_callback),