Add extended command #kick

I've seen some complaints about not being able to kick with ^d
so add kick as an extended command.

Also add the missing #exploremode command to the Guidebook.

doc/Guidebook.tex

@@ -1042,6 +1042,9 @@ Dip an object into something.
 \item[\tb{\#enhance}]
 Advance or check weapon and spell skills.
 %.lp
+\item[\tb{\#exploremode}]
+Enter the explore mode.
+%.lp
 \item[\tb{\#force}]
 Force a lock.
 %.lp
@@ -1051,6 +1054,9 @@ Invoke an object's special powers.
 \item[\tb{\#jump}]
 Jump to another location.
 %.lp
+\item[\tb{\#kick}]
+Kick something.
+%.lp
 \item[\tb{\#loot}]
 Loot a box or bag on the floor beneath you, or the saddle 
 from a steed standing next to you.