Configuration of Protocol Bindings for the cli (`wot-servient`)

Copied from https://github.com/thingweb/node-wot/issues/38.

The cli already uses a `wot-servient.conf.json` for configuration. This should in future also be used to include protocol binding implementations by including entries such as:
```
"servers" : [
"@node-wot/binding-http"
],
"clients" : [
"@node-wot/binding-http",
"@node-wot/binding-coap"
]
```
There can then be required, but we would need standardized class names, I guess.
Is there a better way to do such dynamic dependencies?

Start by inspecting the cli's existing wot-servient.conf.json handling and how protocol binding implementations are currently loaded. The issue does not name files or tests, and its completion criteria remain open: configuration should select server and client bindings, but the dependency-loading and class-name approach still need a decision.

Written by the indexing model from the issue text.