document adding aiida daemon as system service

[ltalirz]

Fixes #1434

[giovannipizzi]

As a note, this will have to change when we merge the workflows branch. @ltalirz could you add a new issue to update the docs when merging? @sphuber is the new way of choosing the file name for the pid compatible with this format for the startup script or do you see problems, as it is generated by AiiDA dynamically?

[giovannipizzi]

Also, @ltalirz would it be possible to generalize it (or suggest what to change to generalize it) to make it work if, e.g., I have two users wanting to start two daemons from two different profiles? (e.g. is changing the syslogidentifier enough?)

[ltalirz]

@giovannipizzi let's move this discussion in the issue #1434

[ltalirz]

@giovannipizzi It seems to me that the feature of running one daemon per profile needs to wait for the workflows branch. I don't think this type of usage is foreseen in release_v0.12.0 (correct me if I'm wrong), so the documentation proposed here should be appropriate.
We'll keep a note in the issue #1434.

Btw, the reason travis fails is due to some reentry changes - I made a note in #1433 to apply fixes to all branches once the problem is fixed.

[giovannipizzi]

Yes correct, this can be merged for 0.12, we just need to keep a ticket open to update it for the next release

[ltalirz]

I'll reopen this; some reentry stuff got in here by mistake.