Ability to reset $isDirty flag

This releases adds the following:

• preventDirtyFlag option
  You can now pass the preventDirtyFlag: true option to any update or insertOrUpdate call to prevent the $isDirty flag from being set to true for this specific action / mutation.

User.update({
    data: myUserToUpdate,
    preventDirtyFlag: true
});

• resetAllDirtyFlags action
  This action will run through all the entities marked as dirty in your store and set the corresponding flag to false.

store.dispatch['entities/resetAllDirtyFlags']({}, { root: true });