Moving away from goamz to use minio-go instead. (#4193)

minio-go does fully managed way of handling S3 API requests

  - Automatic bucket location management across all s3 regions.
  - Transparently upload large files in multipart if file 64MB
    or larger.
  - Right GetObject() API provides compatibility with
    io.ReadWriteSeeker interface.
  - Various other APIs including bulk deletes, server side object
    copy, bucket policies and bucket notifications.

Fixes #4182

config/config.json

@@ -95,11 +95,9 @@
         "AmazonS3AccessKeyId": "",
         "AmazonS3SecretAccessKey": "",
         "AmazonS3Bucket": "",
-        "AmazonS3Region": "",
-        "AmazonS3Endpoint": "",
-        "AmazonS3BucketEndpoint": "",
-        "AmazonS3LocationConstraint": false,
-        "AmazonS3LowercaseBucket": false
+        "AmazonS3Region": "us-east-1",
+        "AmazonS3Endpoint": "s3.amazonaws.com",
+        "AmazonS3SSL": true
     },
     "EmailSettings": {
         "EnableSignUpWithEmail": true,