#1350 Add option to force using the sync PlayerLoginEvent

- Introduce new configuration (taken from @sgdc3)
- Create JoiningPlayer, based on a Player object or String name, determining how permissions will be checked

src/main/java/fr/xephi/authme/settings/properties/PluginSettings.java

@@ -82,6 +82,14 @@ public final class PluginSettings implements SettingsHolder {
     public static final Property<Boolean> USE_ASYNC_TASKS =
         newProperty("settings.useAsyncTasks", true);
 
+    @Comment({
+        "By default we handle the AsyncPlayerPreLoginEvent which makes the plugin faster",
+        "but it is incompatible with any permission plugin not included in our compatibility list.",
+        "If you have issues with permission checks on player join please disable this option."
+    })
+    public static final Property<Boolean> USE_ASYNC_PRE_LOGIN_EVENT =
+        newProperty("settings.useAsyncPreLoginEvent", true);
+
     private PluginSettings() {
     }