Release Notes -- refining new structure

Removed "Monitoring" section; moved ceilometer, mongodb, and zabbix
to "other"

Keystone and Murano also moved to other

1060-general renamed to 1060-openstack; moved one of those issues
to 1030-fuel-install

deleted vestigal 050-known-issues

Change-Id: I028aa9da90e5ef4d4262a71f914ff394c3f413b9