int on_pick(string type, int quantity)

Called on the target object when a player uses the 'pick' command. Returns 1
if the event is defined on the object and it is pickable (such as a plant
bearing fruit).

Type and quantity are useful for specifying what exactly is being picked,
and for picking more than one item at once. The general behavior as defined
in /econ/plant.c is that the event returns 0 if the type string does not
match something that may be picked from the particular plant.

It is left up to the event to handle moving of fruit, etc... but the default
behavior is generally sufficient for most plants.
