[PM-469] Self-contained deployments

Context

We want to store all files related to a service deployment (with the exception of the systemd unit file) in a single location.

What was done

• Move start.sh script into server's install folder instead of the /etc/systemd/system/.d directory
• Modify unit files to use the moved script

TODO

• Merge !15 (merged)

QA

• code was not unit tested, because it's deployment scripts
• acceptance tests were not written, because it's deployment scripts

Review objectives

• assessment of code functionality
• assessment of code quality
• knowledge sharing