Allow setting memory and cpu limits for each docker container run by evaluator

[yuvipanda]

For each docker container we start to run the evaluation, we should specify memory and CPU limits. This prevents rogue files from blowing up memory and cpu usage for the entire infrastructure. Configurable via django settings.

Definition of done

• django settings for specifying memory and cpu limits for each container run
  - [ ] Detect and report 'failed' when they exceed memory limits