Use tabular digits for time labels in public transit route results

The public transit overview, intenerary list, and the list of stops of an expanded transit leg has quite unaligned columns (might depend on the font being used).

It would probably be a good idea to use the "tabular digits" font features attribute for these lables (see placeView.js for an example how to do it programmatically).

To set the attribute from the .ui file, something like:

<attributes>
                <attribute name="font-features" value="tnum"/>
	      </attributes>

should be possible to set inside the definitions for the relevant GtkLables