Single machine tracking issue

[tomwhite]

This is an umbrella issue for tracking the work for making Cubed work better on a single machine.

Processes executor

Improvements to the processes executor

• [x] #507
• [x] #510
• [x] #110
• [x] #515

Threads executor

Improvements to the threads executor

• [ ] #497
• [ ] #511

Accelerators

Work to make Cubed work with GPUs

• [ ] #508

Filesystem

• [x] #512
  • We may need #413 for this
• [ ] #513