Improve cachability of g11n catalog pages.

[mariuswilms]

Originally reported by greut on dev.lithify.me:

What happened:

I wanted to cache Message just like Library (which is cached by default).
it turned out to be difficult because the pluralForm keys are not serializable (see the > workaround below)
What was expected:

to have a nice example of cached g11n by default into the app.
If this one works, it's not very nice…

<?php
// app/config/bootstrap/cache.php
use lithium\g11n\Message;
use lithium\g11n\Catalog;

Dispatcher::applyFilter('run', function($self, $params, $chain) {
    if ($cache = Cache::read('default', 'app.messages')) {
        $cache = (array) $cache + Message::cache();
        $file = Catalog::adapter('lithium');
        foreach ($cache as $scope => &$locales) {
            foreach ($locales as $locale => &$messages) {
                $default = $file->read('message', $locale, $scope);
                $messages['pluralRule'] = $default['pluralRule']['translated'];
            }
        }
        Message::cache($cache);
    }

    $result = $chain->next($self, $params, $chain);

    if ($cache != Message::cache()) {
        $cache = Message::cache();
        foreach ($cache as &$scope) {
            foreach ($scope as &$messages) {
                unset($messages['pluralRule']);
            }
        }
        Cache::write('default', 'app.messages', $cache, '+1 hour');
    }
    return $result;
});