only register services that implement correct interfaces
use isSubclassOf to check for interface usage
Merge pull request #49 from KnpLabs/feature/auto-detect-check-interface

only register services that implement correct interfaces
Merge branch 'develop' of github.com:KnpLabs/KnpRadBundle into develop
Merge branch 'develop' into register-constraint-validator
Added validator constraints dir to watched resources
Prevent registration of validators not extending constraint class