Rework installer

[lhartmann]

This is a reasonably large set of changes, but I broke it up in several small pieces in order to make each step readable.

Changes and improvements:

• Multiple refactoring and de-duplication of code.
• Prefer distribution supplied libmodbus when available.
• Instant swap creation via fallocate (rpi).
• Avoid systemd service files on docker.
• Fix runtime compile warning when EtherCAT was not instaled (rpi, windows, custom).

Tested build, run, launch blank (compile runtime), start and stop on docker/debian:10, docker/fedora:latest, docker/ubuntu:latest.

Untested windows, raspberry pi and EtherCAT.

[thiagoralves]

Thank you for this awesome work on the installer!