Fix markdown and html files and Makefile

Much like the ferguson1/ fixes in the previous commit I have fixed the
lists in the markdown files and the html files have been updated too.

 I *believe* I got the chocolate-cake.html generated properly after
making a change of the chocolate-cake.text (because it's encrypted with
the Enigma and because the judges have their headers/footers I had to
take the generated file from ferguson1 - corrected - and then encrypt it
with the proper key).

Makefile now refers to *.text files rather than *.markdown.

There might be some other changes I forgot.

2020/ferguson2/Makefile

@@ -420,8 +420,8 @@ MAY_NEED_GCC= gcc
 ##############################
 #
 OBJ= prog.o recode.o
-DATA= chocolate-cake.markdown enigma.1 input.txt obfuscation.key \
-	obfuscation.markdown obfuscation.txt recode.1 recode.markdown \
+DATA= chocolate-cake.text enigma.1 input.txt obfuscation.key \
+	obfuscation.text obfuscation.txt recode.1 recode.text \
 	try.this.txt
 TARGET= prog recode
 #