Add maxResultCount optional field to NavtoRequestArgs. Change

session.ts to use this field.  Remove sort of nav items from getNavigateToItems in
sesion.ts because LS now does the sort.  Removed no content throw in
quick info as this happens frequently with Sublime (every cursor move
calls quick info, and quick info is only available on symbols).  Added
mechanism for other commands to avoid throwing and instead return a
specific error message, so that we don't make the log unreadable (as it
was with hundreds of quick info stack traces).

src/server/protocol.d.ts

@@ -676,7 +676,11 @@ declare module ts.server.protocol {
           * Search term to navigate to from current location; term can
           * be '.*' or an identifier prefix.
           */
-        searchTerm: string;
+        searchValue: string;
+        /**
+          *  Optional limit on the number of items to return.
+          */
+        maxResultCount?: number;
     }
 
     /**