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/Pathfinder/CellInfo.cs

@@ -15,7 +15,7 @@ namespace OpenRA.Mods.Common.Pathfinder
 {
 	/// <summary>
 	/// Describes the three states that a node in the graph can have.
-	/// Based on A* algorithm specification
+	/// Based on A* algorithm specification.
 	/// </summary>
 	public enum CellStatus : byte
 	{

OpenRA.Mods.Common/Pathfinder/PathSearch.cs

@@ -219,9 +219,9 @@ namespace OpenRA.Mods.Common.Pathfinder
 
 		/// <summary>
 		/// This function analyzes the neighbors of the most promising node in the pathfinding graph
-		/// using the A* algorithm (A-star) and returns that node
+		/// using the A* algorithm (A-star) and returns that node.
 		/// </summary>
-		/// <returns>The most promising node of the iteration</returns>
+		/// <returns>The most promising node of the iteration.</returns>
 		CPos Expand()
 		{
 			var currentMinNode = openQueue.Pop().Destination;