Correct Attractor spec inconsistencies

[btomaj]

• Transform.apply(graph) was inconsistently also defined as Transform.transform(graph).
• Orphan nodes were inconsistently expected to result in both error and warning.
• run(...) in core execution loop accepted both a context and a config as the second parameter.
• Outcome.status was inconsistently both an enum and a string.
• Edge shape was implied to contain both target and to_node for the same purpose.
• Context behaviour was unspecified for loop_restart=true
• StageStatus==FAIL was inconsistently expected to both terminate and retry.
• wait.human was inconsistently expected to return preferred_label in its Outcome