Sentinel test: tmp dir and gitignore added.
Sentinel: added missing exit(1) after checking for config file.
Sentinel: log +monitor and +set events.

Now that we have a runtime configuration system, it is very important to
be able to log how the Sentinel configuration changes over time because
of API calls.
Sentinel: generate +monitor events at startup.
Sentinel test: removed useless code to set SDOWN timeout.

The new common initialization code used to start a new unit already set
the timeout to 2000 milliseconds.
Sentinel: log quorum with +monitor event.
Sentinel test: more stuff mored from 00-base to init.

The area a number of mandatory tests to craete a stable setup for
testing that is not too sensitive to timing issues. All those tests
moved to includes/init-tests, and marked as (init).