Update Symfony to 2.5.6.
Remove unused use statement.
Merge pull request #8 from SURFnet/maintenance/sensio-insight

SensioLabs Insight fixes
Configure API entity mapping.
Add convenient migration commands.
Add Broadway event stream table.
Add API identity table.
Configure DbalEventStore.
Make sure mapping configuration works in web context.
Configure API projection storage.
Enforce empty public aggregate root constructor.
Correct IdentityCreatedEvent deserialisation.
Exclude Doctrine migrations from scrutinising.
Remove superfluous use statement.
Improve static analysis opportunities of Identity find().
Give Identity a UUID, demote name ID to regular property.
Allow for longer event types, add and drop some indexes.