The bean-validation subsystem should provide a capability; other subsystems should check for it before using classes

JPA and JSF should not use BeanValidationAttachments.VALIDATOR_FACTORY without first checking for a capability.

This will allow JPA and JSF to make their dependencies on the org.wildfly.extension.bean-validation module be optional, which will allow Galleon to skip provisioning the module (and its dependencies) if the subsystem is not configured.