Add an ability to explore current configuration

[3Hren]

Motivation

Currently there is no way to explore current configuration. Imagine a subject that tries to figure out what kind of YANET is configured on a machine:

• How many modules there are. Which kinds of them?
• Which pipelines are currently active with their configuration?

Something like:

> yanet-cli info
Modules:
- route (idx=0)
- forward (idx=1)
- balancer (idx=2).

Pipelines:
  name: pipeline0
  modules:
  - name: forward-from-kernel
    type: forward
  - name: route0
    type: route
  - name: forward-to-kernel
    type: forward

It allows to explore the system and acts as an entry point for further exploration (this is just an example).

> yanet-cli route show
"2a02:6b8::/32":
   source_mac: 52:54:00:12:34:56
   destination: mac: 52:54:00:12:34:ff
"::/0":
   source_mac: 12:34:3a:f4:6e:c2
   destination: mac: 52:54:00:12:34:ff  

However, there is no API to obtain the initial information.

What we need to do?

Implement such API.