Resource needs a toString() method to properly print in debug mode

It would be nice if Resouce had a toString() method so it would print something intelligent rather than simply a memory location in debug mode. (People have complained about this on the Users list, and I've noticed it myself – its annoying.)

Before this change, it prints like:
Resource@8f4fb3

With this patch, it prints like (assuming you accept my FileSet and PatternSet patches):
Resource {targetPath: /target/resource-test, filtering: true, FileSet {directory: null, PatternSet [includes: {}, excludes: {}]}}