Added sprites from OpenTower

- Added sprites from OpenTower as a filler until I make my own
- Added population property to game data
- Renamed gui.gd to gpanel.gd

LICENSE_artwork.txt

@@ -0,0 +1,85 @@
+GROSSINI AND FRIENDS
+--------------------
+
+project/assets/grossini*.png
+
+From:
+   http://www.stortroopers.com/
+
+LICENSE: Attribution-NonCommercial-ShareAlike 2.0
+
+
+SPRITE SHEETS
+-------------
+
+Resoruces/Images/spritesheet*
+
+LICENSE: unsure... don't use them in your project.
+
+
+TILES & TILEMAP:
+----------------
+
+'Barbie Seahorse' tiles:
+    project/assets/tiles.png
+    project/assets/levelmap.tga
+    project/assets/background.png
+
+    From 'Barbie Seahorse' game:
+        http://www.imitationpickles.org/barbie/
+
+    LICENSE: GNU GPL v2
+
+'Hex tiles'
+    project/assets/tilemap/hexa-tiles.png
+    From 'Pioneers' game:
+        http://pio.sourceforge.net/
+
+    LICENSE: GNU GPL v2
+
+'Planet Cute' tiles:
+    project/assets/tilemap/ortho-test1.png
+
+    From Lost Garden:
+        http://lostgarden.com/2007/05/dancs-miraculously-flexible-game.html
+
+    LICENSE:
+        http://lostgarden.com/2007/03/lost-garden-license.html
+
+
+'Spritelib GPL':
+    project/assets/tilemap/fixed-ortho-test2.png
+    project/assets/tilemap/ortho-test2.png
+
+    From 'SpriteLib GPL':
+        http://www.flyingyogi.com/fun/spritelib.html
+
+    LICENSE: Common Public License
+    http://www.opensource.org/licenses/cpl.php
+
+'Tiled examples':
+    project/assets/tilemap/iso_test.png
+    project/assets/tilemap/iso_test2.png
+    project/assets/tilemap/tmw_desert_spacing.png
+
+    From 'Tiled' editor.
+        http://www.mapeditor.og
+    LICENSE: GNU GPL v2
+
+FONTS:
+------
+
+TTF fonts:
+    Resources/Fonts/*.ttf
+    From:
+        http://www.webpagepublicity.com/free-fonts.html
+    LICENSE: For personal Use.
+        
+
+SpriteSheet fonts:
+    project/assets/tuffy_bold_italic-charmap.png
+
+    From:
+        http://tulrich.com/fonts/
+
+    LICENSE: Public Domain