Bring back GuidedDecomp+Closer from the dead, in a good way though

src/main/scala/leon/repair/RepairCostModel.scala

src/main/scala/leon/repair/Repairman.scala

src/main/scala/leon/repair/rules/GuidedCloser.scala

src/main/scala/leon/repair/rules/GuidedDecomp.scala

src/main/scala/leon/synthesis/CostModel.scala

src/main/scala/leon/synthesis/Rules.scala

src/main/scala/leon/synthesis/graph/Graph.scala