Update models to have more relationships and timestamp column definitions.

workflow/engine/src/ProcessMaker/Model/User.php

@@ -7,6 +7,9 @@ use Illuminate\Database\Eloquent\Model;
 class User extends Model
 {
     protected $table = "USERS";
+    // Our custom timestamp columns
+    const CREATED_AT = 'USR_CREATE_DATE';
+    const UPDATED_AT = 'USR_UPDATE_DATE';
 
     /**
      * Returns the delegations this user has (all of them)