Rename Savanna to Sahara

Change-Id: I143d19e6bb5cad5337867964c971878be6965a3a
Imported Translations from Transifex

Change-Id: Iae5d4d962083bc51126298057dff536c27333a4b
Merge "Rename Savanna to Sahara"
Update Sahara (ex. Savanna) glossary term

It based on approved OpenStack Data Processing program mission:

https://github.com/openstack/governance/blob/master/reference/programs.yaml

Change-Id: Icef89781f9a7ae4d07fc7dcc2e08527436c92e4e