Use underscores in chart names

Using hyphens results in non-valid identifiers for values lookup, which makes accessing values awkward.

E.g. to access a value of rucio-daemons in a chart using the the rucio charts as subchart, one has to use:

```
{{ index .Values "rucio-daemons" "value" }}
```

instead of the more straight forward


```
{{ .Values.rucio_daemons.value }}
```
