Updated timestamp algorithm to use Node.matchable, fixing a random bug.
Merge branch 'master' into timefree

Conflicts:
	core/src/main/scala/tbd/TBD.scala
	core/src/main/scala/tbd/ddg/DDG.scala
	core/src/main/scala/tbd/ddg/Node.scala
	core/src/main/scala/tbd/worker/Worker.scala