Each sub-package of pyrosim.legacy should start with vXX, where XX is the last
version (as specified in PyroSimObjectInputStream) where the classes in that
package were used.  

For example, say there is a class called "pyrosim.domain.Foo" and the current 
file version is 39.  Now we want to rename "pyrosim.domain.Foo" to 
"pyrosim.domain.FooBar".  To do this, we increment the file version in 
PyroSimObjectInputStream to 40 and create a new package under pyrosim.legacy
called pyrosim.legacy.v39.domain, and move the old "pyrosim.domain.Foo" class
to this new package.  Then we create a new class called "pyrosim.domain.FooBar"
and make the appropriate handling for the rename in PyroSimObjectInputStream.     