Have gossipd generate node_announcement automatically

[rustyrussell]

1. Change hsmd so gossip can ask for sigs on node_announcement.
2. Pass addresses, color and alias through to gossipd.
3. Have gossipd handle_channel_announcement return true if msg is about us, and new.
4. Move signing code from master to gossipd.

[rustyrussell]

Moved to 0.6, since it's happening with more regularity now.

[cdecker]

Agreed, will slice up the big PR I am currently debugging to fix this first, before addressing #284 which still has a flaky test when running in valgrind

[rustyrussell]

Christian Decker <notifications@github.com> writes:

Agreed, will slice up the big PR I am currently debugging to fix this first, before addressing #284 which still has a flaky test when running in `valgrind`

I've implemented, ran into reproducible gossip problem which is (I think!) pre-existing. Hope to push today...