When set to false, no namespace label will be set by the adapter based on the namespace
portion of the url in the request path.
This allows individual consumers to set namespace independent of the source kubernetes resource.
---
Example:
Given an adapter config like this:
```
externalRules:
- seriesQuery: 'nsq_topic_depth'
resources:
namespaced: false
```
An HPA could target a different namespace by setting it in the selector:
```
- type: External
external:
metric:
name: nsq_topic_depth
selector:
labelSelector:
topic: my-topic
namespace: nsq
```
This is useful for scaling on metrics from services that run in a differnt namespace than the source resource.
According to documentation LabelValuesByName is supposed to render "|" separated values.
Currently it is returned as a slice per label name. This fixes it
Fixes #191
This extracts the label-to-resource conversion to a separte "naming" package for
use across different providers.
Early versions of the commit were done by antoinne85 in #79.
