Remove ambiguity about systemd service files being separate.
Add URL for more information about systemd service files.
Add note about public keys being mandatory for self-signed certs.
Make cert/key file naming consistent throughout document.

Improve documentation for artifact cache installation

See merge request !777

Daniel Silverstone authored Sep 04, 2018 and Tristan Maat committed Sep 04, 2018

The garbage collector can take too long to get around to cleaning
up the Queue and Process instances in completed Job instances.  As
such, FDs tend to leak and in very large projects this can result
in running out of FDs before a build, fetch, track, or other process
can complete.  This patch reduces the chance of that by only creating
the queue when it's needed, and forcing the queue and process instances
to be deleted when the parent is finished with them.

Signed-off-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

jobs.py: Reduce FD leaks from queues and process objects

See merge request !778

Three examples covering out of source builds for:
 * basic autotools
 * basic cmake
 * autotools from a folder inside the source folder

This is also the first cmake example.