CRM-13410 - CiviCase - Add hook_civicrm_caseTypes

Example usage:

```php
function mymodule_civicrm_caseTypes(&$caseTypes) {
  $caseTypes['Example'] = array(
    'module' => 'org.example.mymodule',
    'name' => 'Example',
    'file' => __DIR__ . '/xml/case/Example.xml',
  );
}
```