Removing dynamic mode configuration files can invalidate default mode
setting and/or currently active mode.

If currently selected default mode is no longer available after
configuration file refresh, select "ask" as default mode.

If currently active mode is no longer available after configuration file
refresh, re-evaluate appropriate mode similarly as what is done on cable
connect.

Also document mode names in a bit more detail.
Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>