Improve markdown guidelines wording

Amongst the changes here is that we do not need to have the hex or html
code (numbers) for open and close parentheses (in links) as there are
names. '(' is & followed by lpar; and the ')' is the same but 'rpar;'
instead. This makes it easier to remember and type and it generates the
same html as well (they are all valid). Now the markdown files are
consistent in this (in some cases hex was used and in others the html
code).

Although many markdown files were updated no html files needed to be
updated as it generates the same html. Even so I ran the appropriate
rules to do so just to verify this.

1990/jaw/README.md

@@ -87,7 +87,7 @@ by the receiver. Command shell archives alleviate this problem somewhat, but
 still require standardization for the function of data compression and
 mail-transparency encoding. On Unix, these coding format quandaries are overcome
 by planting a novel [Trojan
-Horse](https://en.wikipedia.org/wiki/Trojan_horse_(computing)) in the archive
+Horse](https://en.wikipedia.org/wiki/Trojan_horse_(computing)) in the archive
 header to perform negotiation-less decoding.
 
 Specifically, we outline the development of an extraordinarily compact portable