Use 'temporary' restart for processes explicitly added to linc_sup

If linc_logic crashes and is restarted by the supervisor, it attempts to
add child processes to linc_sup again (namely ofp_channel_sup,
ofp_conn_listener_sup and linc_us4_sup).  Therefore we need to ensure
that these don't already exist in the supervisor.  Since the linc_sup
supervisor uses the 'one_for_all' strategy, we can ensure that those
child processes go away by using restart type 'temporary'.
Make application stop clear if there's an backend initialization error

So far if there has been an error in sys.config the erlang console
produced a lot of unreadable logs and the linc_sup tried to restart
linc_logic. This had no sense and now the application just stops.
Merge pull request #207 from legoscia/restart-strategies

Attempt to avoid the dreaded no function clause matching linc_us4:stop([])