XD-1816, 1631, 1673: module options asciidoc

This adds a task that will generate a snippet named `asciidoc/guide/modules/<type>.<module>.asciidoc` for each module, that we can then simply include from the main asciidoc documentation like so:
```
include::modules/<type>.<module>.asciidoc[]
```

This way, documentation is always up to date.
Note that:
* we can choose to selectively NOT include the file and stick with our current way of doing on a per module basis
* we can generate the files locally from time to time and push them to the github wiki repo, so that the wiki also has content
* the asciidoc `include` macro accepts attributes that we may leverage if we want _e.g._ to not generate doc for some options, or provide additional text for some options

An example rendering is [here](https://gist.github.com/ericbottard/5eb03086ed8dba9d0591)