Feature: Support ChimeraTK::Void (and potentially ::Boolean)

There is currently no automatic conversion for Void to something understood by OPC-UA, so those variables are skipped.

Would be nice to have them handled as well in some way, though probably not strictly necessary.

```
Cannot proxy unknown type ChimeraTK::Void for variable Devices/APPUIO/deviceBecameFunctional
Cannot proxy unknown type ChimeraTK::Void for variable manual/trigger
```