MinIO: Bug fix and feature release.

### Highlights - **Experimental & Non Production Use**: Added Backblaze B2 Gateway support. - Bring back support for **Docker/Harbor Registry**. - Figure out projectID for GCS automatically from credentials.json - Support creating **empty directories** on FS backend. - **CopyObject** API now preserves metadata in S3 gateway mode. ### Changelog - Support for bosh/pcf user-agent when querying for updates. (#5116) (20 hours ago) <Krishna Srinivas> - "0" offset is ignored in GetObject method in Azure Gateway code (#5118) (21 hours ago) <kannappanr> - GCS gateway to return error in getBucketPolicy, when no policy is set (#5117) (21 hours ago) <kannappanr> - convert ETag properly for all gateways (#5099) (29 hours ago) <Bala FA> - Use retryableStorage after healing format.json (#5105) (29 hours ago) <Aditya Manthramurthy> - Fix s3MetaToAzureProperties Content-Md5 key (#5068) (2 days ago) <Julien Maitrehenry> - log: Store http request/responses in a log file (#4804) (2 days ago) <A. Elleuch> - Set etag properly to calculated value if available (#5106) (3 days ago) <Harshavardhana> - Update documenation to reflect correct default region of '' (#5101) (4 days ago) <kula> - Update azure.md (#5086) (5 days ago) <asubmani> - Simplify data verification with HashReader. (#5071) (6 days ago) <Harshavardhana> - Move packages between dependencies and devDependencies (#5094) (7 days ago) <Krishna Srinivas> - Fix multipart upload etag on azure gateway (#5055) (7 days ago) <Julien Maitrehenry> - Figure out projectID for GCS automatically from credentials.json (#5029) (7 days ago) <Krishna Srinivas> - Fix notification unmarshalling, unmarshal only when size is > 0 (#5087) (7 days ago) <Harshavardhana> - Fix typo in comment (#5088) (8 days ago) <Frank Wessels> - Remove unused packages from vendor.json (#5079) (9 days ago) <Krishna Srinivas> - fix: Avoid teeing data into a null cache buffer (#5070) (9 days ago) <A. Elleuch> - Ignore file not found error for multipart-uploads (#5065) (9 days ago) <Nitish Tiwari> - Do not attempt to generate URLToken for anonymous downloads (#5078) (10 days ago) <Harshavardhana> - fs: All parts except the last part should be of the same size (#5045) (10 days ago) <Krishna Srinivas> - Fix gateway docs remove redundant files (#5072) (11 days ago) <Harshavardhana> - Remove NotSupported error redundant with NotImplemented (#5074) (11 days ago) <Harshavardhana> - Support creating empty directories. (#5049) (11 days ago) <Harshavardhana> - Implement backblaze-b2 gateway support (#5002) (2 weeks ago) <Harshavardhana> - Remove go1.9 specific code for windows (#5033) (2 weeks ago) <Harshavardhana> - Remove body from POST request in webhook (#5067) (2 weeks ago) <Nitish Tiwari> - Fix azure metadata handling for all incoming PUT requests (#5038) (2 weeks ago) <Harshavardhana> - Update docker swarm doc to use docker volume prune (#5053) (2 weeks ago) <Nitish Tiwari> - Fix data race bug in the testcase TestHTTPListenerAcceptParallel (#5043) (2 weeks ago) <Krishna Srinivas> - pkg/http: use port 65432 than 9000 for unit tests (#5021) (2 weeks ago) <Bala FA> - Update Minio version in docs and example yaml files (#5054) (2 weeks ago) <Nitish Tiwari> - Move Dockerfile to go 1.9.1 (#5047) (2 weeks ago) <Harshavardhana> - Add b2s method on pkg/disk/type_bsd.go (#5036) (3 weeks ago) <Julien Maitrehenry> - tests: Remove dependency on check.v1 (#5034) (3 weeks ago) <Harshavardhana> - Move to go1.9.1 as default environment. (#5041) (3 weeks ago) <Bala FA> - Move gateway unsupported functions into a common struct. (#5009) (3 weeks ago) <Harshavardhana> - Refactor update check code (#5020) (3 weeks ago) <Aditya Manthramurthy> - S3 peers should be initialized properly (#5024) (3 weeks ago) <Harshavardhana> - fix build failure for go1.9 (#4872) (3 weeks ago) <Bala FA> - Return errors in PutObject()/PutObjectPart() if input size is -1. (#5015) (3 weeks ago) <Harshavardhana> - Enable ListMultipartUploads and ListObjectParts for FS (#4996) (3 weeks ago) <Krishna Srinivas> - Fix healthcheck issue with Docker containers (#5011) (3 weeks ago) <Harshavardhana> - remove all dead codes (#5019) (3 weeks ago) <Bala FA> - Translate s3 gateway errors at object layer (#5006) (3 weeks ago) <Krishnan Parthasarathi> - verify: add minio gateway s3 setup for verification tests (#4976) (3 weeks ago) <Bala FA> - Allow CopyObject() in S3 gateway to support metadata (#5000) (3 weeks ago) <Harshavardhana> - Push max threads to little less than kernel limit (#5001) (3 weeks ago) <A. Elleuch> - fix: List buckets response should return UTC modtime (#5004) (3 weeks ago) <A. Elleuch>