- Save model doesn't work after the user creates elements (e.g. a
  port) in a PtalonActor from Vergil.

- User is not notified of invalid parameters or ports after a
  parameter change of the PtalonActor. 

- We may want to remove ports that are unconnected on the outside of a
  PtalonActor after a parameter change.  Test this by creating a demo
  that has a PtalonActor with a parameter that sets the number of
  ports.

- Model parameters that are used in a Ptalon file but are not declared
  as actual PtalonParameters may not get their values transferred to a
  PtalonActor at the right time, unless they happen to change values
  at the same time as a declared PtalonParameter.
  - Here is a test:
  1. Comment out the range paramter in SmallWorld.ptln
  2. Also remove the range parameter in SmallWorld.xml
  3. Open SmallWorld.xml in Vergil and set top level range parameter to 100 in SmallWorld.xml
  4. Open PtalonActor to verify that node radius sizes have not changed.
  5. Run model.
  6. Change range parameter to 50.
  7. Open PtalonActor to verify that node radius sizes have or have not changed.
  8. Do the same steps above, but first uncomment the call to validateSettables() in Manager.preinitializeAndResolveTypes().
  9. Verify that results of model are the same, even though visually, the radii may be different.

- MapReduce demo doesn't work when the number of machines equals 1.

- paser.g: It is unclear that BOOLEAN_FACTOR, BOOLPARAMETER, etc are needed.

- Need test framework for structural changes tested in ptalon/test/*.ptln

- "actorparameter" vs. "actor" keyword is not enforced by the Ptalon compiler.

- Is "transparent relation" really needed?

- SharedParameters don't work.  
  - For an example, use one of the ptinyos demos in the ptalon demo
  directory and removed the timeResolution parameter from the DE
  Director of all submodels (keep the top-level timeResolution
  parameter).  timeResolution is a shared parameter which should get
  propagated to the other DE Directors.
  - Another example is to remove the commandPort and nodeID parameters
  from the submodels (fill in parameter values in PtinyOSDirector with
  default values).