Adds support for indexed key arguments and escaped dot arguments to `--state-values-set`.
Things like `--state-values-set config\.yml.something=abc` or `--state-values-set config.something[0]=abc` can be passed in the command line.
Resolves#899
This adds `values` to state files as proposed in #640.
```yaml
values:
- key1: val1
- defaults.yaml
environments:
default:
- values:
- environments/default.yaml
production:
- values:
- environments/production.yaml
```
`{{ .Valuese.key1 }}` evaluates to `val1` if and only if it is not overrode via the production or the default env, or command-line args.
Resolves#640