Fixed Symfony 2.8 deprecations

[King2500]

See: https://github.com/symfony/symfony/blob/2.8/UPGRADE-2.8.md

• Fixed FormTypeInterface::getName deprecations
• Fixed using deprecated form names instead of full-qualified class names
  Solution for backwards compatibility is similar to what FOSUserBundle did: https://github.com/FriendsOfSymfony/FOSUserBundle/blob/master/Util/LegacyFormHelper.php
• All changes also applied to the tests.
  They ran OK on my machine (Win7, PHP 5.6.20, PHPUnit 5.3.2, Sf 2.8.4)

[merk]

Thanks!