disallow config.yaml with no options entry
Merge pull request #78 from rogpeppe/031-require-config-options

disallow config.yaml with no options entry
WIP actions fix: recurseMapOnKeys tested
Actions formatting tightened up

Charm now expects a much simpler format for actions.yaml:

```yaml
<action name>:
  [description]: <string>
  [params]:
  [required]: <string list>
```