Closes#824
This implements statistics gathering across the various components, but
ultimately this is for implementing a new CLI command: `container
stats`. This shows memory usage, cpu usage, network and block i/o and
the number of processes in the container. The new command can inspect
stats for 1-N containers and by default continuously updates in a `top`
like stream.
## Type of Change
- [ ] Bug fix
- [x] New feature
- [ ] Breaking change
- [ ] Documentation update
## Testing
- [x] Tested locally
- [x] Added/updated tests
- [x] Added/updated docs
Danny Canter