Review StyleCop rules.

- Enforce SA1604 ElementDocumentationShouldHaveSummary.
- Enforce SA1629 DocumentationTextShouldEndWithAPeriod.
- Turn off some rules covered by IDExxxx rules.
- Remaining rules are treated as part of OpenRA style.

OpenRA.Game/Actor.cs

@@ -587,7 +587,7 @@ namespace OpenRA
 			return InvalidConditionToken;
 		}
 
-		/// <summary>Returns whether the specified token is valid for RevokeCondition</summary>
+		/// <summary>Returns whether the specified token is valid for RevokeCondition.</summary>
 		public bool TokenValid(int token)
 		{
 			return conditionTokens.ContainsKey(token);