Support Signature V4 for S3

[tim-semba]

This PR supports Signature Version 4 for S3. Some examples use V4 now.

It should replace #199. Some codes have been copied from #199, my thanks to @angerman .

[tim-semba]

How well have you tested this?

I have tested below (both of s3UseUri is True and False patterns):

• S3.PutBucket
• S3.DeleteBucket
• S3.Multipart
• S3.GetObject
• S3.GetBucket
• S3.GetBucketLocation
• S3.PutObject
• S3.CopyObject
• S3.DeleteObject

I believe other APIs are well, because of this is independent of a specific API.