debugfs: create inode_dump command to dump an inode in hex

debugfs: create inode_dump command to dump an inode in hex

Create a command that will dump an entire inode's space in hex.

[ Modified by tytso to add a description to the man page, and to add
  the more formal command name, inode_dump, in addition to short
  command name of "idump". ]

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>