(nukstr): Make it a struct genitem: add members nuk_effic, nuk_mobil,

nuk_tech, nuk_stockpile, nuk_opx, nuk_opy, nuk_mission, nuk_radius.
These have no effect, yet.
(build_nuke): Initialize them.
(nuke_ca): Add genitem selectors: effic, mobil, tech, group, opx, opy,
mission, radius.
(tran_nuke): Zap mission, just in case somebody invents missions for
nukes.
(trade_desc): Show tech and efficiency, for consistency with other
units.

src/lib/commands/tran.c

@@ -133,6 +133,7 @@ tran_nuke(void)
 	/* TODO apply dam */
 	nuke.nuk_x = dstx;
 	nuke.nuk_y = dsty;
+	nuke.nuk_mission = 0;
 	putnuke(nuke.nuk_uid, &nuke);
     }
     if (mcost > 0)