Revert "implemented file / directory .close()"

This reverts commit 83b4470fc94a179cccfc2daf16042493dcf12132.

Revert the additional close() methods, as those are already available via the
namespace.entry class -- with a colliding method signature

Please open tickets if close() still fails on any package/adaptor which
inherits from namespace.
Merge branch 'devel' of github.com:saga-project/saga-python into devel