Search bar: make clearing text easier

[graue]

Fixes #244:

When you change your mind about where you were going and want to enter a new destination, it is annoying to have to clear the LONG text strings like

Réveille Coffee Co., 200 Columbus Avenue, San Francisco, 94133

that get put in there by the geocoder.

Focusing the start or end input will now select all contents, if the text is unmodified text from the geocoder. We were already doing this for the text "Current Location." There is no select all if you have hand-edited the text.