debugfs: clean up debugfs man page and help text

Clean up the formatting of the debugfs(8) man page:
- add command aliases to the main descriptions
- use bold for sub-commands and italics for their arguments
- remove trailing spaces
- add "dirty" sub-command
- clarify "block_dump" and "zap_block" sub-commands

Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
3 files changed