KList updates
KList updates

 - exchange variance annotations on KList for a bounded existential
   in KList.toList
 - add foldr (reason for dropping variance annotations)
 - add functions stating equivalence between
   + KList[M,H :+: T] and KCons[H,T,M]
   + KList[M,HNil] and KNil

Duhemm/util,xuwei-k/xsbt,sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,mdedetrich/sbt,xuwei-k/xsbt,xuwei-k/xsbt,sbt/sbt,mdedetrich/sbt,xuwei-k/xsbt,xuwei-k/xsbt,mdedetrich/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,sbt/sbt,sbt/sbt,sbt/sbt