Minor fixes

Set all SS logs to use storage_service.log.  Set default
Space.staging_path to /var/archivematica/storage_service/
Move path mangling to Space

move_to_storage_service expects the source path to be absolute, and the
destination path to be absolute inside the staging path.  Since this is
common, move it to Space.
Swift: Fill out stubs

refs #6938

Implement browse, delete, move to/from for Swift.
Swift: Add tests

Add tests for browse, move_to and delete.  Problems with VCR.py recording
responses for move_from.  Manually set expires time for auth key to year
3000 to prevent replay issues.
Swift: Support folders

refs #6938

Add support for interacting with folders in Swift. Swift only stores objects
and fakes having folders, so use prefix and delimiter paramaters to deal
with this.