Improved installation procedure

Description

Current installation procedure is sub-optimal.

Tasks

• Create a check-dependencies script that checks whether the needed commands are available.
• Rename the provision command to install-dependencies (keep the old name as a symlink).
• The install-dependencies should check the operating system type before installing dependencies.
• Compilation of vendorized applications should happen in runtime (like with mkp2240), not during installation (like with the current way onion-csr is compiled).
• Make CI test onion-csr.
• Take the opportunity to fix and improve whatever is easy and quick to do.
• Update the documentation.

Time estimation

• Complexity: very small (0.5 day)
• Uncertainty: low (x1.1)
• Reference (adapted)

cc: @gus