Modifiable output [Enhancement]

[evilmonkey19]

At the moment, all the outputs will remain the same. For example, if we issue display board, it will be always the same output. Even though, for v1 it works and enough, for v2, it would be awesome to be able to set the output dynamically based on a variable (similar to Server-side rendering and jinja2). The idea as that at startup and at runtime that output it is able to change depending on the input or some other external events.

This idea is related to create a fake network. For example, if someone creates two routers which are linking on startup and it issues the command show link 0, it should say active up. Later, if we issue a command like do command link down, then the router that who set the link down, when doing a show link 0 it should show a Disabled. In the other router should say as well first up and then down.