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
0.5.0 introduces a new way to configure the containers and execs. This
is now done all upfront at constructor time in a callback style. I'm
very happy with the config improvements, but because IO can only be
setup at constructor time this makes it so that we need to supply IO at
creation time of the VM or exec, which isn't the end of the world. All
that really changes is `boostrap()` and `createProcess()` now take in IO
instead of slightly later in `process.start()`
Danny Canter