Implement and document ;set and ;unset interface

ape/talk.hoon

@@ -1045,12 +1045,21 @@
       ++  wo-set                                        ::  %set
         |=  seg=span
         ^+  ..sh-work
-        ..sh-work
+        ?~  seg
+          %+  sh-fact  %mor
+          %+  turn  (~(tap in settings.she))
+          |=  s=span
+          [%txt (trip s)]
+        %=  ..sh-work
+          settings.she  (~(put in settings.she) seg)
+        ==
       ::
       ++  unset                                         ::  %unset
         |=  neg=span
         ^+  ..sh-work
-        ..sh-work
+        %=  ..sh-work
+          settings.she  (~(del in settings.she) neg)
+        ==
       ::
       ++  target                                        ::  %target
         |=  [lix=?((set partner) char) woe=(unit ^work)]

pub/docs/user/talk.mdy

@@ -238,7 +238,7 @@ most recent; etc.
 
 ### Nicknames
 
-<mark>Not yet implemented</mark>
+<mark>Partially implemented</mark>
 
 Sometimes you know your Urbit friends by other names, on or
 offline.   Use the `;nick` command to assign or look up
@@ -255,6 +255,10 @@ someone you know by a nickname.  Just type `~plato`, and `:talk`
 will replace it magically with `~fintud-macrep` (or beep if no
 `~plato` is bound).
 
+If you would prefer to see nicknames instead of urbit names when
+someone speaks, use `;set noob`. `;unset noob` disables this
+setting.
+
 ### Presence
 
 You'll see presence notifications when people enter or leave
@@ -302,3 +306,12 @@ To ban from `%bizarre-board`:
 To appoint a coauthor of `%serious-journal`:
 
     ;author %serious-journal ~lagret-marpub
+
+### Settings
+
+To set a frontend option in your `talk` session, use `;set
+[option]`, or `;unset [option]` to unset it. To see all currently
+set options, just type `;set`. The options available are:
+
+- `noob` - Display user-defined nicknames instead of ship names
+  if available.