Why do we have objects for joint training?
https://github.com/IllinoisCogComp/saul/blob/master/saul-core/src/main/scala/edu/illinois/cs/cogcomp/saul/classifier/JointTrain.scala
https://github.com/IllinoisCogComp/saul/blob/master/saul-core/src/main/scala/edu/illinois/cs/cogcomp/saul/classifier/JoinTrainSparseNetwork.scala

How are they different? Do we want to somehow merge them?