Drools should allow the default target to be specified outside the rule file

Drools should allow the default target to be specified outside the rule file. This allows common rule sets to be reused across different process flows.

A common use case for this requirement is using Drools as a semantic validator. In this case, each rule in the rule set generates a fault if it is satisfied. If no rule is satisfied, the message is considered valid and forwarded to the externally-supplied default target. The rule file used to implement this semantic validator can be re-used across many process flows.

When implementing a semantic validator as described above, it would also be useful for each rule to optionally forward "fault content" to the default target instead of generating a JBI fault. In this case, the default target would be responsible for distinguishing between fault and non-fault content and handling it appropriately. A convenience method added to the JbiHelper, such as faultToDefaultTarget(), would significantly help a rule writer implement such functionality.

I intend to submit a patch for this issue in the near future.