Adds the ability to include relations when using the UpdatedAt observer

[emlynwest]

Putting this up here to get thoughts on the feature/implementation. I thought this would be a useful feature as often an ORM entity consists of multiple models.

My example is that a blog post has many "i18ns", translatable data stored in a separate table (so another model), when any of the i18ns are updated I want to be able to reflect that change on the parent blog post. This observer will allow this to work.

$blog_post->i18ns[$i18n_id]->title = 'My new title';
$blog_post->save();
// $blog_post->updated_at is now "now()"

The added setting is used like this:

protected static $_observers = array(
    'Orm\\Observer_UpdatedAt' => array(
        'events' => array('before_save'),
        'mysql_timestamp' => true,
        'property' => 'updated',
        'relations' => array(
                'i18ns',
        ),
    ),
);

Docs are on the way.

[WanWizard]

docs ? ;)

[emlynwest]

As usual something exploded and needed to be fixed. I'll try and get the PR for the docs up today.

[emlynwest]

fuel/docs#599 for docs.

[emlynwest]

Just need to fix an issue of not being able to handle has_one or belong_to