fixing namespaces and PHPDoc

lib/private/connector/sabre/exception/invalidpath.php

lib/private/connector/sabre/node.php

lib/private/connector/sabre/objecttree.php

lib/private/files/view.php

tests/lib/connector/sabre/directory.php

tests/lib/connector/sabre/exception/invalidpathtest.php

tests/lib/connector/sabre/file.php

tests/lib/connector/sabre/node.php

tests/lib/connector/sabre/objecttree.php