Move the savanna subdir to sahara

Rename the subdirectory and replace all instances
of "import savanna" with "import sahara" and all
instances of "from savanna" with "from sahara".

* Replaced mock patches like mock.patch('savanna...
* Updated config generator script
* Renamed entry points in setup.cfg
* Hacking checks also fixed
* Manual renaming in alembic scripts to force work migrations
* Fix doc building
* Renamed itests directories
* Some changes in gitignore
* Removed locale dir after rebase

Co-Authored-By: Alexander Ignatov <aignatov@mirantis.com>

Change-Id: Ia77252c24046c3e7283c0a7b96d11636020b949c
Partially implements: blueprint savanna-renaming-service