base: added national roaming info for Play in Poland

http://jira.omnirom.org/browse/OMNI-105

Users of Play in Poland (MCC 260 MNC 06) can roam on
Plus, T-Mobile, Orange (MNCs 01/02/03)

Change-Id: I8ea62b0ca40bac9ced11802ee8ef583d6392a199