Core: Support URN and URI Namespaces?

To catch up Faces itself, migrate XML namespaces as well:

`http://primefaces.org/ui --> primefaces.ui`

### Current:
```xml
xmlns:p="http://primefaces.org/ui"
```

### To:
```xml
xmlns:p="primefaces"
```

Hopefully there is a clever way to support both?
