Tidy up the DB Event logger, add failsafe

If there is a problem with the Model, don't try to log with a broken model (infinite loop), this can be confirmed by checking if the Model class alias exists

modules/system/ServiceProvider.php

@@ -6,7 +6,6 @@ use Event;
 use Config;
 use Backend;
 use Request;
-use DbDongle;
 use Validator;
 use BackendMenu;
 use BackendAuth;
@@ -244,7 +243,7 @@ class ServiceProvider extends ModuleServiceProvider
     protected function registerLogging()
     {
         Event::listen('illuminate.log', function ($level, $message, $context) {
-            if (DbDongle::hasDatabase() && !defined('OCTOBER_NO_EVENT_LOGGING')) {
+            if (EventLog::useLogging()) {
                 EventLog::add($message, $level);
             }
         });

modules/system/models/EventLog.php

@@ -1,7 +1,8 @@
 <?php namespace System\Models;
 
 use Str;
-use Model;
+use DbDongle;
+use October\Rain\Database\Model;
 use Exception;
 
 /**
@@ -22,6 +23,19 @@ class EventLog extends Model
      */
     protected $jsonable = ['details'];
 
+    /**
+     * Returns true if this logger should be used.
+     * @return bool
+     */
+    public static function useLogging()
+    {
+        return (
+            class_exists('Model') &&
+            DbDongle::hasDatabase() &&
+            !defined('OCTOBER_NO_EVENT_LOGGING')
+        );
+    }
+
     /**
      * Creates a log record
      * @param string $message Specifies the message text