JCLOUDS-457: Add JobStatus enum

Now the job status is stored as an enum instead of
a String. This is useful when comparing the status to
check if a job is completed, failed or still in progress.
JCLOUDS-457: BlobStore Skeleton

The Amazon Glacier BlobStore skeleton has been added.
JCLOUDS-457: Fix complete MPU archive size

The completeMultipartUpload operation is taking the archive size
parameter in MB but it should be bytes.
JCLOUDS-457: BlobStore MultiPartUpload strategy

The code related to the MultiPartUpload strategy has been added.
MultiPart uploads use an upload strategy (e.g. sequential vs parallel)
and also a slicing strategy to split the payload in different parts.