3.0 split utility

This set of changes make Utility completely independent of the rest of CakePHP. It introduces one change that needs to be reflected in the app template as `Configure` is no longer used inside this namespace.

Applications will need to add this to the bootstrap:

```php
Security::salt(Configure::read('Security.salt'));
```
Should we have a requirement on ext/xml, ext/mbstring and ext/dom?