upgrade: full orchestration from I.1.1.0 to I.1.2.0

Orchestrate the upgrade from I.1.1.0 to I.1.2.0 on Debian for all nodes.
upgrade: fix README for I.1.2.0

Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge pull request #79 from enovance/upgrade-1.2.0

upgrade: full orchestration from I.1.1.0 to I.1.2.0