Enable running post build publishers.

Post build publishers like ext-email-plugin are run in the cleanUp()
method. Add this method to NWDIBuild.RunnerImpl. Add getAffectedFiles() to
DtrChangeLogEntry.
Remove usedDCs from ComponentWrapper that don't need rebuilding.

This prevents the case where components would not be rebuilt because of
dependencies further up in the depedency chain:

- DC changed but
- depending on another DC not changed in this build.