Created most of the general framework. The OuranosFileSystem will
delegate to various OuranosFileStores. Each OuranosFileStore will be a
separate cloud service for file storage. Tests cannot be written for
OuranosFileSystemProvider until I figure out how to implement
#getFileStore(Path).

OuranosPath takes after *nix paths. The separator is '/' and currently
the only root directory is '/'. .. is the parent directory and . is the
current directory.