Correct short git commit hash in version string to be at the beginning of the full hash, not the end

SpritePacker/Program.cs

@@ -40,7 +40,7 @@ namespace SpritePacker
 		public static int Main(string[] args)
 		{
 			string commitHash = Utilities.GetEmbeddedResourceContent(commitHashFilename).Trim();
-			Version += "-" + commitHash.Substring(commitHash.Length - 7);
+			Version += "-" + commitHash.Substring(0, 7);
 
 			for(int i = 0; i < args.Length; i++)
 			{