Moving walkthros up a level in TOC (rebased onto dev_5_0)



This is the same as gh-963 but rebased onto dev_5_0.

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See https://trello.com/c/TsgYDWGJ/191-server-installation-links
Now we have the installation docs listed in a separate index there is less need to 'hide' the walkthroughs to cut down on clutter. This should make them easier for the relevant people to find and they already have clear text at the top of each page to make sure sysadmins are clear on the content and which doc they need to read for which system.