Scheduler adaptor for slurm webservice

[sverhoeven]

Currently bartenders slurm scheduler adaptor is using ssh to call slurm commands.

It would be nice if bartender could talk to the slurm web service (https://slurm.schedmd.com/rest.html).

Gotchas:

• token for slurm web service still has to be generated on slurm node
• web service might not be accessable, so ssh tunnel or request from slurm node is needed