Add starting_up_state parameter to Updater

[redvinaa]

In the current implementation, when the Updater object is constructed, it sends off an "OK" signal. This could be problematic if we consider "Everything is running as expected" (definition of "OK" status as per REP107), that running is already initialized.

The default behavior doesn't change with this PR, so it wouldn't break anything. Also, in the python implementation, None can be passed to skip "Node starting up" status publishing altogether.