Conventional schedulers (Slurm/PBS/Loadleveler) compatibility?

Nobody has claimed this yet.

**Is your feature request related to a problem? Please describe.**
Most supercomputers in the world use of the few schedulers available, like the ones mentioned at the title. Those usually don't play well with other schedulers.

**Describe the solution you'd like**
To be able to run it directly from a slurm session.

**Describe alternatives you've considered**
In many SPMD environments, one is able to submit one single program to run in a number of compute nodes. So, this program should be able to run as a master in one node, and as a worker in all the other nodes. Something like a front-end to mars.

**Additional context**
Supercomputer schedulers are quite simple in operation. The user submits a job to the batch system, which waits until the amount of resources requested is available. Then, it runs the code in all the processes. It's that simple.

No files, tests, or entry points are named. The issue asks for Mars to run directly from a Slurm session and mentions Slurm, PBS, and Loadleveler compatibility; first define the supported scheduler behavior and integration boundary, then verify that a submitted multi-node job can start the requested master and worker processes.

Written by the indexing model from the issue text.