Add importer validator for Views.

Updated issue summary.

It appears to be that the argument in the path "/import/%/log" is already validated. This happens in views/feeds_views_handler_argument_importer_id.inc. It is that only the wrong action is taken when the argument is not valid. It should be "Show page not found" and not "Display contents of no result found".

A validator for "/node/%/log" indeed is needed. Now a "Log" tab shows up for every node, even when that node is not a feed node.

The attached patch does the following:

• It adds a Views validator for "feed_nid". This expects a node id and will validate if there is an importer attached to the node's type.
• For "/import/%/log", the action to take when the argument validation fails is set to "Show page not found".
• For "/node/%/log", the validator is set to "feed_nid" and the action to take when the argument validation fails is set to "Show page not found".
• It adds translations for the View (automatically exported by Views).

Side node: the Log view could be improved more. See #1393898: Order Log view by flid instead of log_time.

Awesome work on Feeds, twistor!

How did you get the translatables export?

Because I see these translatables always when I export a View, I thought they were added by default. Further exploration learns me that they are only exported when the core module "Locale" is enabled (or when Views' localization plugin gets overridden, see below), which I have enabled by default because I usually install my sites in Dutch.

From views/includes/view.inc, method export(), ± line 1917:
Views uses its localization plugin to export translatables.

// Give the localization system a chance to export translatables to code.
if ($this->init_localization()) {
  $this->export_locale_strings('export');
  $translatables = $this->localization_plugin->export_render($indent);
  if (!empty($translatables)) {
    $output .= $translatables;
  }
}

From views/views.module, ± line 1351:
The localization plugin can be overridden.

/**
 * Load the current enabled localization plugin.
 *
 * @return The name of the localization plugin.
 */
function views_get_localization_plugin() {
  $plugin = variable_get('views_localization_plugin', '');
  // Provide sane default values for the localization plugin.
  if (empty($plugin)) {
    if (module_exists('locale')) {
      $plugin = 'core';
    }
    else {
      $plugin = 'none';
    }
  }

  return $plugin;
}