Output of dry run improved

The Output of --dry-run was confusing, because it only listet the "array_keys" which have been just numbers. In the unfortunate case, that only one message was added this resulted in an output like : "Added Messages: 0". 
Therefore are now the real number of added messages shown and with --verbose option even the message IDs with initial "desc" translation.

Comment on composer.json:
As I wanted to test my code I came across the issue that an old version of di-extra-bundle (1.0.1) was loaded. This version has no dependency on aop which caused exceptions, due to the fact that the AOPBundle is loaded in the FunctionalTest AppKernel.php