Motivation:
A typical (POSIX) filesystem has only one unique identifier for a file,
so called inode number. However, dCache as inumber and a corresponding
pnfsid. As being originally developed as a part of dcache, nfs4j have
inherited that and exposes as Stat#ino and Stat#fileid. After some
iterations, only `fileid` is used, and `ino` kept as 32 bit version of
it.

Modification:
drop Stat#get/setFileId methods in favor of Stat#get/setIno (for better
compliance with POSIX). Update `ino` to 64 bit long. Update codebase to
use `ino`.

Result:
less confusions with a price of small incompatibility with earlier
versions.

Acked-by: Lea Morschel
Acked-by: Paul Millar
Target: master