remove unused constants

These constants have been moved to different projects

Author: gdaniel

src/main/java/com/xatkit/core/recognition/IntentRecognitionProviderFactory.java

@@ -48,15 +48,6 @@ private IntentRecognitionProviderFactory() {
      */
     public static final String LOGS_DATABASE = "xatkit.logs.database";
 
-    /**
-     * The default value for xatkit.database.model in case it's not specified in the properties file.
-     */
-    public static final String DATABASE_MODEL_MAPDB = "mapdb";
-
-    public static final String DATABASE_MODEL_POSTGRESQL = "postgresql";
-
-    public static final String DEFAULT_DATABASE_MODEL = DATABASE_MODEL_MAPDB;
-
     /**
      * The intent provider that will be used for this instance of Xatkit.
      * <p>