Allow jobs associated only through fingerprinted files to appear in the

dependency graph. This functionality is enabled through a feature flag,
hudson.tasks.Fingerprinter.enableFingerprintsInDependencyGraph, which is off
by default.

- Rebuild the dependency graph as part of each fingerprint action.
  Fingerprinter.buildDependencyGraph adds information to the dependency graph
  for projects found in fingerprint records. Since the dependency graph is
  based on project, once a relationship is established between two projects,
  we can skip scanning subsequent builds of the projects. Entries in the
  graph added by the fingerprinter action will never automatically trigger
  downstream builds.

   core/src/main/java/hudson/tasks/Fingerprinter.java

- When reporting dependency changes, don't consider builds that no longer
  exist. This handles issues when projects are renamed, and new projects are
  created using the same name, causing the change to point to incorrect
  builds.

   core/src/main/java/hudson/model/AbstractBuild.java

- Tests.

   test/src/test/java/hudson/tasks/FingerprinterTest.java