Replace catsplosion plugin with a script

Closes DFHack#938, DFHack#722

catsplosion.lua

@@ -0,0 +1,97 @@
+-- Make cats just /multiply/.
+--[[=begin
+
+catsplosion
+===========
+Makes cats (and other animals) just *multiply*. It is not a good idea to run this
+more than once or twice.
+
+Usage:
+
+:catsplosion:           Make all cats pregnant
+:catsplosion list:      List IDs of all animals on the map
+:catsplosion ID ...:    Make animals with given ID(s) pregnant
+
+Animals will give birth within two in-game hours (100 ticks or fewer).
+
+=end]]
+
+world = df.global.world
+
+if not dfhack.isWorldLoaded() then
+    qerror('World not loaded.')
+end
+
+args = {...}
+list_only = false
+creatures = {}
+
+if #args > 0 then
+    for _, arg in pairs(args) do
+        if arg == 'list' then
+            list_only = true
+        else
+            creatures[arg:upper()] = true
+        end
+    end
+else
+    creatures.CAT = true
+end
+
+total = 0
+total_changed = 0
+total_created = 0
+
+males = {}
+females = {}
+
+for _, unit in pairs(world.units.all) do
+    local id = world.raws.creatures.all[unit.race].creature_id
+    males[id] = males[id] or {}
+    females[id] = females[id] or {}
+    table.insert((dfhack.units.isFemale(unit) and females or males)[id], unit)
+end
+
+if list_only then
+    print("Type                   Male # Female #")
+    -- sort IDs alphabetically
+    local ids = {}
+    for id in pairs(males) do
+        table.insert(ids, id)
+    end
+    table.sort(ids)
+    for _, id in pairs(ids) do
+        print(("%22s %6d %8d"):format(id, #males[id], #females[id]))
+    end
+    return
+end
+
+for id in pairs(creatures) do
+    local females = females[id] or {}
+    total = total + #females
+    for _, female in pairs(females) do
+        if female.relations.pregnancy_timer ~= 0 then
+            female.relations.pregnancy_timer = math.random(1, 100)
+            total_changed = total_changed + 1
+        elseif not female.relations.pregnancy_genes then
+            local preg = df.unit_genes:new()
+            preg.appearance:assign(female.appearance.genes.appearance)
+            preg.colors:assign(female.appearance.genes.colors)
+            female.relations.pregnancy_genes = preg
+            female.relations.pregnancy_timer = math.random(1, 100)
+            female.relations.pregnancy_caste = 1
+            total_created = total_created + 1
+        end
+    end
+end
+
+if total_changed ~= 0 then
+    print(("%d pregnancies accelerated."):format(total_changed))
+end
+if total_created ~= 0 then
+    print(("%d pregnancies created."):format(total_created))
+end
+if total == 0 then
+    qerror("No creatures matched.")
+end
+print(("Total creatures checked: %d"):format(total))