OpenHPC 2 support and more flexible host naming

Now has support for:

• CentOS 8 and OpenHPC 2
• CentOS 7 and OpenHPC 1.x

List nodes and partitions in slurm.conf using ansible inventory group contents rather than assuming they follow a stricter naming scheme.

Bugfixes and updates

• Improve logic for restart handlers.
• Provide options for setting maximum job runtime.
• Support single-node partitions in slurm.conf.
• Fix grouping logic for installation of lmod package.

Toggle between drain and resume

Merge pull request #10 from stackhpc/drain-resume

Drain/resume toggle (v0.4.0)

v0.3.0: Merge pull request #8 from stackhpc/client-support

Enable the definition of clients to Slurm