Add a command for port configuration

[pavel-kirienko]

Currently, to set up a port or to check its configuration, one has to type a lot of characters:

$ y r 125 uavcan.pub.dynamics.id
65535

$ y r 125 uavcan.pub.dynamics.id 120
120

This should be improved with a dedicated helper command ("L" is for "link"):

$ y l 125 p dynamics            # Displays the port:type tuple per standard notation
65535:zubax.physics.dynamics.DoF3rdTs.1.0

$ y l 125 p dynamics 120        # Changes and displays the result
120:zubax.physics.dynamics.DoF3rdTs.1.0

$ y l 125 p                     # Display all publishers on this node as a dict
dynamics: 120:zubax.physics.dynamics.DoF3rdTs.1.0
dq: 65535:zubax.telega.DQ.1.0
...

$ y l 125                       # Display all ports on this node
pub:
  dynamics: 120:zubax.physics.dynamics.DoF3rdTs.1.0
  dq: 65535:zubax.telega.DQ.1.0
sub: ...
cln: []
srv: ...
...