Preserve metadata across copy-in-the-cloud
Clarify du behavior for file/object hierarchies

.
Properly elide subdirectories in du -s when the argument is a subdirectory.
Write hashing test files in binary mode for Windows compatibility
Release notes for 4.5
Update CHECKSUM and VERSION for 4.5 release.
Hashing refactoring
Fix test_naming tests that were not resilient to list ordering.
Fix TypeError during perfdiag
Retroactively call out hash format change in 4.0
Make top-level gsutil help consistent with gsutil help options
Allow gsutil static temp file directory to be configurable, deprecate resumable_tracker_dir
Refactor BucketListingRef to make it more polymorphic.
Convert BucketListingRef and StorageUrl getters to properties.

* Make XmlPassThrough functions take a StorageUrl.
* Rename BucketListingRef.TypeName() to .type_name.
* Rename GetVersionlessUrlStringStripOneSlash to CreatePrefixUrl.
* Fix a few linter warnings.
Added proxy_rdns param to boto config support and plumbed through to support clients that disallow DNS lookups
Add StorageUrl as a member of BucketListingRef and NameExpansionResult.

- Then use them where it makes sense to.
- Simplify NameExpansionResult.
Don't attempt perfdiag DNS lookups if DNS lookups are disabled in boto config
Silence unit test output.

When running unit tests (e.g. gsutil test -u), stderr and log output is no
longer spewed to the terminal. If you would like to see the stdout, stderr, and
logging output, you can run with gsutil with the -D flag.
Only attempt to delete uploaded perfdiag files if a write test ran
Fix invalid refs to constants introduced in 681dc4636d4ec009870fbbf99fd00ff538c97ed4