User-friendly options menu

Make the default options menu only show the most important
options, split into categories. The full, traditional menu
can be accessed by using the m-prefix.

doc/Guidebook.tex

@@ -962,6 +962,7 @@ a further menu or prompt will appear once you've closed this menu.
 The available options
 are listed later in this Guidebook.  Options are usually set before the
 game rather than with the `{\tt O}' command; see the section on options below.
+Precede {\tt O} with the {\tt m} prefix to show advanced options.
 %.lp
 \item[\tb{\^{}O}]
 Show overview.\\
@@ -1494,6 +1495,7 @@ Open a door. Default key is `{\tt o}'.
 %.lp
 \item[\tb{\#options}]
 Show and change option settings. Default key is `{\tt O}'.
+Precede with the {\tt m} prefix to show advanced options.
 %.lp
 \item[\tb{\#overview}]
 Display information you've discovered about the dungeon.  Any visited