Not finalized Unit Interface

This is the only interface I'm unsure if I want to keep the same.  I don't think we will get any use from returning values on these functions considering what we're using them for.

Also, it may be best to get rid of EffortUnit, TimeUnit, CostUnit and place the getters and setters in Unit interface.
Less error prone that way if a new type is added. IE RewardPoints or something.