There are a few rough edges, but it is now reasonably safe to unload and
reload MVC in Squeak trunk.

Unloading:

  Smalltalk zapMVCprojects.
  (MCPackage named: 'ToolBuilder-MVC') unload.
  (MCPackage named: 'ST80') unload.
  ScheduledControllers := nil.
  Smalltalk garbageCollect.

Reloading:

  Load package ST80
  Load package ToolBuilder-MVC
  Evaluate "MVCToolBuilder compileAll".

Issues:

- MVCToolBuilder needs to be recompiled after reloading. I have not yet
  found the reason, but something still needs to be fixed here.

- MVC itself is still badly broken, and has been since about Squeak 3.8.
  Nothing that I did changes that.

- The new methods in category "editors" in class Project should probably
  be moved to UIManager.

- All senders of Project>>dispatchTo:addPrefixAndSend:withArguments: should
  be updated to use ToolBuilder, and the #dispatchTo:addPrefixAndSend:withArguments:
  mechanism should be removed.

Dave