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.
Converted frequency-table to a dock window.
Auto select row in frequency-table.
Support more Freq-Tables and selecting via Combobox.
small changes to frequency-list.
Stub of frequency scanner
Merge branch 'master' into bookmarks

Conflicts:
	gqrx.pro
New bookmark system. Bookmarks are now shown in plotter.
Merge branch 'master' into bookmarks

Conflicts:
	applications/gqrx/mainwindow.cpp
	qtgui/plotter.h
Merge branch 'master' into bookmarks
Merge remote-tracking branch 'steven/scanner' into mine

Conflicts:
	applications/gqrx/mainwindow.cpp
Merge remote-tracking branch 'steven/bookmarks' into mine

Conflicts:
	applications/gqrx/mainwindow.cpp
	applications/gqrx/mainwindow.h
	gqrx.pro
Fixed saving of bookmarks, somewhat