[ietf-clear] Re. CLEAR Charter

I made a number of edits, which you may find at 
http://wiki.fastmail.fm/wiki/index.php/ClearCharter .
Some comments:
I added 'mainstream' because IIRC, CSV requires a valid FQDN in HELO.  
Alternate text could invoke best practices: s/existing mainstream usage 
and operations practices/BCP/.

Diff:
http://wiki.fastmail.fm/wiki/index.php/ClearCharter?action=diff