Further refactorings of BEJob and BEJobID.

[vinjana]

• Removed parentJob and parentJobID constructor parameters. Only the parentJobs remain, as the jobs contain the information isDirty, required by client code. Instead parentJobIDs and parentJobs can now be set by two (fluent) addParentJob[s,IDs] methods.
• Instead of silently selecting one of parentJobIDs or parentJobs in the constructor, client code (Roddy) now has to reconciliate lists of Jobs and IDs (see there)
• BEJob.getJobID now returns IDs, not Strings.
• Further array job code was removed, e.g. to simplify the BEJob constructor.

[vinjana]

I suggest I merge this now, even though there is still some work the interface. Changing the Job as parameter of the BEJobID and related classes seems like a larger undertaking :-(