Changed to use regular heading instead of pathHeading because regular
heading uses GPS info when available but then the path info when not. So
it is more likely be set to a usable value.
Changed filtering out of matches due to not having sufficient heading
info. Previously was filtering out non-layover matches if heading not
available. But this was causing vehicle to match to a layover into the
future, which is not at all desirable. Therefore changed the code so
that matches are filtered out due to heading not being available only
once best temporal match has been determined.