Update guide from 7.0 to 7.1

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Point installation manual to 7-1-stable

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Version to rc1

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Update guide from 6.0 to 7.1

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'release-candidate' into 'master'

Release candidate

* add 7.0-7.1 update doc
* add 6.0-7.1 update doc
* update installation doc
* Bump version

Part of #1435

See merge request !977