copy generated docs (if build) into help bundle

Improvement for documentation build with a singe command:

just build

```
mvn clean install -Pproduct,sdk,docs
```
and docs will be build with ```sphinx-build``` prior help bundle. The help bundle just unpack the prepared zip file, containing the user docs with simple style, and apply content to help bundle structure (toc.xml & ./EN folder)

Requirement: Sphinx build environment (with python), see docs/pom.xml fo details.