winrtrunner: Support Windows Phone 8.1

This allows the runner to deploy to Windows Phone 8.1 devices
and
emulators.

The following limitations are noted:
- App argument passing doesn't currently work. A workaround
could be to
  modify the entry point in the AppxManifest.xml, which would
also
  require changes to qtmain. WP8.0 already uses a similar
workaround,
  but this is messy and should be avoided if possible.
- Querying for the application state doesn't work, so -wait
won't exit
  if the app stops. A workaround for this exists in WP8.0, by
passing
  the -qdevel parameter to the app, but this is invasive. If
an
  alternative can't be found, this can be fixed in a follow-
- Stopping applications doesn't appear to work (the API call
succeeds,
  but the app remains running). One workaround is to -remove
the app.
- Getting the exit code still isn't possible.

Task-number: QTBUG-37771
Change-Id: Ifa7188fc2ccb156e4c411b50fefd4f12a0590883
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>