Current stable guides show the "Guides Index" links without underline,
just showing it when it's hovered. This restores the same functionality
for edge guides.

Also remove annoying pointer cursor while accessing guides index,
restoring previously functionality: now the pointer cursor only appears
when hovering a link.

Closes #8107 [ci skip]

Previously this code just assumed it is capable of changing the file
ownership, both user and group. This will fail in a lot of scenario's
unless:
* The process is run as a superuser (root);
* The owning user and group are already set to the user and group we're
  trying to chown to;
* The user chown'ing only changes the group to another group it is a
  member of.
If either of those conditions are not met the filesystem will simply
deny the operation throwing an error.

It is also not always possible to do a chmod, there might be a SELinux
policy or another limitation preventing the user to change the file
mode. To this end the chmod call has also been added to the rescue
block.

I've also added a little comment above the chmod command that doing a
chmod on a file which has an ACL set will cause the ACL to be
recalculated / modified.

Changed comment section to be more explicit. I had an issue with rolling back a migration and couldn't understand why 'rake db:reset' didn't work.

Fixed in the JS guide in 8c38172b

This reverts commit 507e522e.

Revert "Explain where the acronym AJAX stands for & replace "JavaScript writer" with "JavaScript developer""

This reverts commit 1332cf53.

This reverts commit a6d383c8.

This reverts commit 6d927fb4.

This reverts commit 506257a1.

We discussed this on Twitter, seems to be the best option.

I believe the topics and their headlines should be consistent for obvious reasons. Also

This is similar to #first_or_create, but slightly different and a nicer
API. See the CHANGELOG/docs in the commit.

Fixes #7853