Deploy an app inside a web template in SharePoint 2013

The main objective is to deploy an app inside a web template, so when I create a sub site using that template, the app will be included. To do that, I have followed this Microsoft blog, but I have no luck.

The steps I have followed are:

1. Create a new site and save it as a template.
2. Download the template as a wsp file
3. Change wsp extension to cab
4. Extract the cab content and modified the onet.xml file adding the following lines::

<!--XXX app Feature-->

<Feature ID="{62300948-B52A-445D-BE0D-477B10E00CEE}" Name="FeatureDefinition/15/62300948-B52A-445D-BE0D-477B10E00CEE" SourceVersion="0.0.0.0" />

5. Reassemble the wsp file using DDFGenerator and the MakeCab sentence.

6. Upload the wsp file into SharePoint solutions

7. Now, when I create a sub site using the web template that I have modified this error displays:

Please, anyone could help me? I have done an extensive research but I haven't found any clue.