Good beginner doc-hacking task: clear-text vs. cleartext vs. clear text vs. plaintext etc..

While working on a docs patch I realized that we use a wide variety of
terminology for secrets that will not be encrypted, which is very different
from secrets which will be encrypted; the former is IMO cleartext and the
latter plaintext.

In the documentation, when we talk about secrets used for passwords
authentication and similar, we use a mix of "clear-text", "cleartext" and
"clear text"; in at least one place we also use "plaintext". There are several
cases where we use "plaintext password" correctly, but we also have the variant
"plain text" vs, "plain-text" vs. "plaintext" there as well.

It would be nice to get that cleaned up and consistent, but I don't intend to
spend time on it myself. However, I know from attending a session on
documentation at PGConf.EU that there are several potential contributors who
would like to work on the docs but don't know exactly where to start, so I
figured I'd raise it here as a good introductory project.

If someone does take a stab at it, I will of course spend the time to review
it.

--
Daniel Gustafsson