sysadm: add life-cycle-management section

sysadm/life-cycle-management/how-to-manage-tools-upgrades.rst

+How to manage upgrades of tools and software inventory
+======================================================
\ No newline at end of file

sysadm/life-cycle-management/how-to-new-service-backup.rst

+How to devise the backup strategy for a (new) service
+======================================================
\ No newline at end of file

sysadm/life-cycle-management/index.rst

+Life-cycle management
+=====================
+
+.. toctree::
+   :maxdepth: 2
+   :titlesonly:
+
+
+   how-to-manage-tools-upgrades
+   how-to-new-service-backup