Add retry options

[MrCreosote]

Add options to retry save / get calls for the workspace and the blobstore.

For the workspace, might want to add a load ID to the object metadata (or make the workspace support it directly) to make it easy to check if the object you expected was loaded.

[MrCreosote]

May require nasty exception string parsing to avoid retrying certain to fail operations, like too much data or too much memory used for sort. This might be easier if we added exception codes to the workspace and the blobstore