2.5 load all

This is how the loadAll method should intuitively work.
If global defaults are set, they should be respected as long as they are not specifically overwritten by a specific plugin config.

For me it is not sound that having global `bootstrap => true` suddenly doesnt work anymore just because for a plugin I add `routes => true`, as well.
```php
CakePlugin::loadAll(array(
		array('bootstrap' => true), // For all plugins
		'Pdf' => array('routes' => true)
));
```
Would not load the bootstrap for Pdf now.

This would be needed, which seems overhead to me:
```php
CakePlugin::loadAll(array(
		array('bootstrap' => true), // For all plugins
		'Pdf' => array('routes' => true, 'bootstrap' => true) // Even though we said we want bootstrap for all plugins
));
```

This is the intuitive way when we don't want the global config for a specific plugin:
```php
CakePlugin::loadAll(array(
		array('bootstrap' => true), // For all plugins
		'Pdf' => array('routes' => true, 'bootstrap' => false)
));
```