S3 credentials via URL options

In addition to env variables parse the S3 credentials from URL options. Following options are supported:

• s3_access_key
• s3_secret_key
• s3_auth_region

Example CLI:

arcls "s3+https://mys3.example.com;s3_access_key=key1234;s3_secret_key=secret1234/mybucket/"

Example xRSL:

( inputFiles =
   ("myfile" "s3+https://mys3.example.com/mybucket/myfile" "s3_access_key=key1234;s3_secret_key=secret1234")
)