Merge pull request #9389 from senny/forwardport_9388

Forwardport #9388 rename/remove column preserves custom PK.
adds a missing LIMIT 1 in #take docs
guides/rails_guides moved up and out of the railties directory
Merge pull request #9393 from rubys/master

guides/rails_guides moved up and out of the railties directory
registers the encrypted session store in the AP changelog
prevent minitest from printing a --seed run option

See the first FIXME comment in the patch for the rationale.
Revert "prevent minitest from printing a --seed run option"

Reason: on a second thought, minitest prints a seed as run option
regardless of the test order, and it actually calls srand, so
albeit it might be misleading I believe, it is the way it is and
should be left that way.

This reverts commit c15862ae0cb876d745609170f0f90a9bb9b5e0ae.
also rename the test-case class inside columns_test.rb
Merge pull request #9394 from senny/actually_rename_the_test_case

also rename the test-case class inside columns_test.rb
Oracle enhanced adapter shortens its name if it is longer than 30 bytes
because of Oracle database index length spec.
Merge pull request #9395 from yahonda/oracle_index_length

Address failure test_rename_column_with_multi_column_index with Oracle
test case to prevent duplicated associations with custom PK.

closes #9201