N5Factory add make s3 ClientConfiguration customizable

[bogovicj]

see saalfeldlab/n5-aws-s3#31

[kgabor]

Another issue in an EMR-serverless environment was authentication "token expiration" errors when a spark task runs for several hours. This is related to assumed roles in the EMR-serverless environment. The suggested workaround is to use a custom credentialsProvider in setting up the S3Client. Beside the ClientConfiguration it'd be nice to have flexibility in customizing the credentialsProvider as well. Attached the suggested singleton S3Manager class solution by AWS support for both the token expiration and for the slowdown error issues mentioned in 31. (I am not sure, this may need the upgrade to AWS SDK v2.)

emr-spark-demo.zip