Codegen and java compile now use artifact cache.
Bugfix.
Bugfix in zinc artifact copyiong.
Refactor and debug dependency analysis.

Almost a complete rewrite of the dependency analysis. The new code is
more modular, more functional, and most importantly, more correct.

Also modified the ZincAnalysisCollection to take analysis file specs
that identify the target class directory associated with an analysis file.

Auditors: benjy
Addressing review comments.