The grains example would traceback if the grain was not defined, so I
have replaced this example with a better one. Also made a few changes
for consistency in formatting, and made a couple terms into links to the
relevant documentation.
This commit modifes a number of files which have command-line examples
so that the code-block directive is used. This provides more
visually-appealing syntax highlighting.
More commits like this will follow, this commit is part of an overall
documentation audit that I am performing.
