Refactor restconf-nb blueprint wiring

The blueprint serves three purposes:

• dependency injection
• configuration injection
• component wiring

While we cannot deal with the first two just now, we should move component wiring into Java and just inject dependencies/configuration.

This will result in WebInitializer being replaced with JaxRsNorthbound class, which handles all the details of wiring classes.

Conversion to Declarative Services will then be a simple matter of dropping annotations are removing the blueprint.