knowledge-base: retract an accepted record or its clauses on the operator's Approve

The operator prefers removing a wrong decision to stacking a correcting
record on it, and withdraw took only reserved or proposed records. retract
asks the operator through the router like a record that needs the operator,
and changes nothing until the Approve; a retracted record or clause no longer
holds in ask, holds, get, links and progress, history keeps every version, and
the whole-set rules still read a retracted record's links so a retraction alone
raises no finding. withdraw with retraction true takes a waiting one back.

modules/mesh-knowledge/module.json

@@ -33,6 +33,7 @@
         "import",
         "return",
         "withdraw",
+        "retract",
         "progress"
       ]
     }
@@ -54,6 +55,7 @@
         "import",
         "return",
         "withdraw",
+        "retract",
         "progress"
       ]
     }