Provide hooks to configure `cri-dockerd` via a configuration file

Similar to other CRI and CNI providers, the amount of possible churn in cri-dockerd in keeping up with upstream k8s may become a lot, and shifting around defaults in command-line args is not a great experience for consumers.

viper is already part of the deptree (though we'll pull a new version), and we can relatively easily expose NetworkPluginSettings, ContainerRuntimeOptions, and the small amount of daemon-specific options while keeping reasonable defaults.

Additionally, this would allow for all of these to easily be set/tweaked via environment variables if desired.

TOML is not the greatest format in the world, but it's reasonably well supported by burntsushi/toml into viper, with headings as above (daemon-specific options as top-level/without subkey).

@afbjorklund input?

Start with config/types.go, config/options.go, and cmd/cri/options/options.go to map the existing option structs and defaults. Review how viper and TOML support fit the dependency tree, then define configuration loading and environment-variable behavior while preserving defaults. Done means the daemon-specific, network-plugin, and container-runtime options can be configured as proposed and are covered by tests.