Documentation updates
Documentation updates

* Installation instructions are now on kernelci-backend-config

This patch remove duplicate ansible instructions and give a link
to the right kernelci-backend-config github

* Add some administration informations

Signed-off-by: Corentin LABBE <16a2fc074d33dba14e47b55c74beb641d5160cd9@baylibre.com>

kernelci/kernelci-backend,kernelci/kernelci-backend