Added Giant Rat portrait by ZygoUgo (manual merge of PR #1715)

I cleaned up the transparent areas of the image, increased height to a more standard 200px and moved the ARTISTS file entry to the right spot.

data/core/about.cfg

@@ -680,6 +680,10 @@
         name = "Vincent Langner (Vyncyn)"
         comment = "Walking Corpse and Soulless wolf variations"
     [/entry]
+    [entry]
+        name = "ZygoUgo"
+        comment = "Giant Rat portrait"
+    [/entry]
 [/about]
 
 [about]

data/core/images/portraits/ARTISTS

@@ -185,6 +185,9 @@ thespaceinvader/Philip Barber and LordBob/Emilien Rotival:
 bera/Bora Orcal and Kitty/Kathrin Polikeit:
     Goblin Spearman
 
+ZygoUgo:
+    Giant Rat
+
 Outdated versions:
 
 Jason Lutes:

data/core/units/monsters/Giant_Rat.cfg

@@ -4,6 +4,7 @@
     name= _ "Giant Rat"
     race=monster
     image="units/monsters/giant-rat.png"
+    profile="portraits/monsters/giant-rat.png"
     hitpoints=15
     movement_type=rodentfoot
     movement=4