Split customisable elements from generated ones

[stefanogermano]

Is your feature request related to a problem? Please describe.

The sections in WIDOCO are designed to separate things you might want to customise from things you usually don't (because they are automatically generated)
The Introduction section seems to contain both because it also contains the namespaces table.
That is not the best when you want to write the introduction text only once (and then somehow keep in the following generations) since the namespaces used can change.

Describe the solution you'd like

Clearly separate content you might want to customise (the introductory text) from content you usually don't (the namespaces table).