further work for contracts to use interfaces instead of abstract classes

Changes include:

- a new ProjectorInterface for the Projector abstract class
- CommandHandling and ReadModel scenarios to use interfaces rather than abstract classes
Add support for parameter
Minor tweaks from running php-cs-fixer

php-cs-fixer --verbose fix src
   1) Broadway/Bundle/BroadwayBundle/DependencyInjection/BroadwayExtension.php (trailing_spaces, extra_empty_lines)
   2) Broadway/Bundle/BroadwayBundle/Resources/config/saga/in_memory.xml (trailing_spaces)
   3) Broadway/Bundle/BroadwayBundle/Resources/config/saga.xml (trailing_spaces)
   4) Broadway/EventSourcing/EventSourcedEntityInterface.php (phpdoc_params)
   5) Broadway/EventSourcing/Testing/Scenario.php (new_with_braces)
   6) Broadway/EventStore/EventStoreInterface.php (phpdoc_params)
   7) Broadway/Repository/AggregateNotFoundException.php (phpdoc_params)
   8) Broadway/Saga/MultipleSagaManager.php (unused_use)
Merge pull request #60 from mbadolato/php-cs-fixer_tweaks

Minor tweaks from running php-cs-fixer
Merge pull request #48 from Miliooo/compiler

RegisterBusSubscribersCompilerPass: Add support for parameter return values
Merge pull request #40 from brightmachine/2-contracts-using-interfaces

further work for contracts to use interfaces instead of abstract classes
CommandHandler fix
Merge pull request #35 from Miliooo/loop

CommandHandler avoid endless loop
Implementing Aggregate Factory

This work is comprised of changes from both @simensen and @kelvinj and taking
into account a lot of discussion on IRC. Squashed 7 commits into one.
Change ordering of aggregate factory argument and make it mandatory.
Merge pull request #44 from simensen/aggregate-factory

Aggregate factory
Remove usage of `should` in test method names betterspecs.org/#should