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.