Installation: Refactor installation process only based on setup.py

[mpeuster]

The vim-emu layer is Python only and does not require additional modules like Containernet does. Thus we should refactor the installation process and only rely on the setup.py. Would also allow to distribute the vim-emu package as pypi package.

• update setup.py
• use requirements.txt
• update setup-cli.py (do we really need it?)
• update ansible installer to only call setup.py