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.Mods.Common/Activities/FindAndDeliverResources.cs

@@ -152,7 +152,7 @@ namespace OpenRA.Mods.Common.Activities
 
 		/// <summary>
 		/// Finds the closest harvestable pos between the current position of the harvester
-		/// and the last order location
+		/// and the last order location.
 		/// </summary>
 		CPos? ClosestHarvestablePos(Actor self)
 		{