Dockerfile: Multidocker based on Ubuntu 20.04

* Switchable build arg versions
* Scancode build from releases, not from python npip
* Python uses pyenv. Default python is 3.8.11
* Nodejs is using nvenv.  Default nodejs is the latest LTS
* Ruby uses rbenv. Bundler and Cocoapods now come by default
* Wrapper script to use bashrc on direct ort usage
* Use bash and pipefail on all operations as default. Exception for
Android sdkmanager that behaves differently on pipefail
* Silence gpg dearmor output on tee
* Using a single downloader, curl
* Go updated to last stable release

Signed-off-by: Helio Chissini de Castro <helio@kde.org>