link quality attribute

[nicoechaniz]

It's good to have a normalized 0 < quality < 1 to represent this in the link line on the map, but seeing the actual quality value is usually very important.

I propose to add a quality_attr member to the base data structure for links.

For example:

   {
       "type": "wifi",
       "alias_local": "64:70:02:3D:85:0B",
       "alias_remote": "64:70:02:EE:02:E8",
       "quality": 0.25,
       "quality_attr": "signal",
       "attributes": {
           "local_mac": "64:70:02:3D:85:0B",
           "station_mac": "64:70:02:EE:02:E8",
           "channel": 165,
           "signal": -81,
           "interface": "wlan1"
       }
   }

This would let us show the actual quality value (in this case the signal value) in the link popup.