More cleaning up LinkTaskManager code

refs #4757

Removing unused imports and variables, code that doesn't do
anything or is unused.
archivematicaClient announces new transcoder rules

refs #5575

Archivematica client doesn't announce old (CommandRelationship based)
transcoder rules, but new (fpr_fprule) rules.  Also updated Django
definition of TaskConfig and MicroServiceChainLink for better print
display and matching SQL better.