Document what variables are set based on the API Blueprint file

We would like to write our own templates with custom appearance, but it is slightly cumbersome at this moment due to the fact we need to read all the used variables in example files. While we already managed to workaround the situation, it would be nice to document the features and data that are extracted from the Blueprint file, such as:
- self.api.navItems
- self.api.resourceGroups
- self.api.metadata
- ...