Mixin for Ember models. Adds metadata properties that can be used to resolve synchronization conflicts. Creation and changing date and time of record will be filled with current date and time on model saving. It's recommended to use this mixin when model class extends subclass of DS.Model or includes other mixins, i.e. it's not inherited directly from DS.Model. Also it can be used explicitly when it is not necessary to use projections for particular model in application. If model class inherited directly from DS.Model and it's planned to use projections, then it's recommended to extend model class from Offline.Model.