The containers require Internet connection at startup for pulling Community Modules

[unclev]

Steps to implement:

• [ ] Modify update-modules.sh so that it can clone/update files in a specified location;
• [ ] At build time clone the initial snapshot of the community modules - store them separately for further use;
• [ ] At start up copy modules from the image if community modules folder appears to be empty.

Even though with this approach community modules may be not up to date, but they would be

• taken at the same time as a prosody package installed within the container;
• can be updated by issuing docker exec update-modules as before.