Adds a list of Frequencies which you can click on to tune to it.

The list is read from (on Linux) : ~/.config/gqrx/frequency-list/radio.csv

The File List looks like this:

```
 98500000, Bayern3     , WFM       , 400000
 99000000, Oe3         , WFM       , 122000
105700000, Bayern 5    , WFM       ,
```

Modulation and Bandwidth are not yet used.