Expand system resources specs

Nobody has claimed this yet.

Currently we have::

```
sys_variables = {
"sys_cores_per_node": 64,
"sys_gpus_per_node": 8,
"sys_mem_per_node": 512,
}
```

`sys_mem_per_node` may need to be replaced by::

```
sys_host_mem_per_node
sys_device_mem_per_node
```

Another needed addition::

```
sys_hw_threads_per_core
```

The allocation modifier should default to one thread per core, and the user should be able to use some multiple of hardware threads per core.