Accept `locale` as config value for GET parameter

You may need to run functional scenario against specific localization.
Now you can do it by passing `locale` configuration to OpenMVC Module.
Sample `functional.suite.yml`:

```
class_name: TestGuy
modules:
  enabled: [Filesystem, TestHelper, OpenMVC]
  config:
    OpenMVC:
      locale: 'en'
env:
  en:
    modules:
      config:
        OpenMVC:
          locale: 'en'
  ru:
    modules:
      config:
        OpenMVC:
          locale: 'ru'
```

Now if you run `codeception run functional --env ru` you will only run
tests that are configured to run in Russian environment. Here is an
example of functional cest that tests both English and Russian localized
versions of app:

```
<?php

class HomeCest
{

    /**
     * @env en
     */
    public function verifyThatEnglishLoginLinkLeadsToLoginPageInEnglish($I) {
      $I->amOnPage('/');
      $I->click('Login');
      $I->seeInCurrentUrl('/en/login');
    }

    /**
     * @env ru
     */
    public function verifyThatRussianLoginLinkLeadsToLoginPageInRussian($I) {
      $I->amOnPage('/');
      $I->click('Войти');
      $I->seeInCurrentUrl('/ru/login');
    }

}
```