Rejig the Translation panel controls and documentation to remove the emphasis

Rejig the Translation panel controls and documentation to remove the emphasis
on received data. Experiment and suggestion suggest that the character set
configuration applies equally to keystrokes sent to the server, or at least
that that's close enough to being true that we should document it as a first
approximation.

git-svn-id: http://svn.tartarus.org/sgt/putty@8209 cda61777-01e9-0310-a592-d414129be87e