ImportDependency

[Bryan Atsatt]

The design of this class seems broken to me with the addition of two 
"types". Why not:

1. Make ImportDependency abstract, removing the getType() and newX methods.
2. Make ImportPackage and ImportModule subclasses, each with their own 
newX method.

(I also strongly suggest that we rename ImportDependency to simply 
"Import" :^)

This model also obviously enables new subtypes, an extensibility point 
that may come in handy in the future.

// Bryan