The patch:
1. Updates the 'Set up a local repository' section
of the Fuel Install Guide to replace the deprecated
`fuel-createmirror` command with the current
`fuel-mirror` one;
2. Moves this file to a separate section since it
seems to be not related to the 'Upgrade' section;
3. Fixes noticed typos.
Closes-Bug: #1651737
Partial-Bug: #1563086
backport: newton mitaka
Change-Id: I523ec8c6d5341a51fbdf555f1e9e0dfbab875770