Failing tests for umask
EntryCreationContext: add a FileAttribute<?>[] as an argument

It is necessary in order to convey the real permissions of the file instead of
the umask.
Make umask the way it is supposed to work, nearly...

It works OK when creating a file, creating a file with attributes and creating a
directory WITHOUT attributes.

However it fails when creating a directory with attributes, reason unknown.
Merge pull request #45 from fge/topic/umask

Attempted fix at the umask problem