Make cache expiration configurable

Core/src/main/java/com/plotsquared/core/configuration/Settings.java

@@ -527,6 +527,13 @@ public class Settings extends Config {
         public static int TARGET_TIME = 65;
     }
 
+    @Comment("Settings related to tab completion")
+    public static final class Tab_Completions {
+        @Comment({"The time in seconds how long tab completions should remain in cache.",
+                 "0 will disable caching. Lower values may be less performant."})
+        public static int CACHE_EXPIRATION = 15;
+    }
+
 
     @Comment({"Enable or disable parts of the plugin",
         "Note: A cache will use some memory if enabled"})

Core/src/main/java/com/plotsquared/core/util/TabCompletions.java

@@ -56,7 +56,9 @@ import java.util.stream.Collectors;
 public class TabCompletions {
 
     private final Cache<String, List<String>> cachedCompletionValues =
-        CacheBuilder.newBuilder().expireAfterWrite(15, TimeUnit.SECONDS).build();
+        CacheBuilder.newBuilder()
+                .expireAfterWrite(Settings.Tab_Completions.CACHE_EXPIRATION, TimeUnit.SECONDS)
+                .build();
 
     private final Command booleanTrueCompletion = new Command(null, false, "true", "",
             RequiredType.NONE, null) {};