integrated_image formtype is broken in 0.7

Steps to reproduce

• Go to /admin/channel/new

• Result: Exception

I expect the merge of to be the reason, but I am not sure (version 0.6 does not have this problem). Maybe it is because Symfony 2.8 needs the FQCN (https://github.com/symfony/symfony/blob/2.8/UPGRADE-2.8.md#form).