We didn't specify that the db user needs the right to create
temporary tables before.
That's why the migration will fail on most installations.
This commits removes the "TEMPORARY" from the migration
and changes the documentation to include the necessary rights for the future.

[ci skip]

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This reverts commit 5daf44b7, reversing
changes made to 2f706fbd.

This reverts commit 957e849f, reversing
changes made to 6b9dbe9f.
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This reverts commit 8a01a122.

Even though the 7-12-stable branch does not exist yet.

Git 2.1.2 does not protect against pushes trying the '.Git/config'
attack (CVE-2014-9390). Going to 2.4.3 is perhaps a big jump but why not
use the latest? (Famous last words.)

https://www.ruby-lang.org/en/news/2015/04/13/ruby-2-1-6-released/

Rephrased wording in the documentation to say "installation from source" instead of  "manual installation" or similar.

product names, plus a couple of instances of bad Markdown markup.

closes #8718, closes #8721