Add more documentation for create_join_table.

Explain that it doesn't create indices by default and
that it also has a block form.
Fix warning
Indent comment block by two spaces.

As requested by @fxn
https://github.com/schuetzm/rails/commit/743d15bba182df80d003d205690ead988970299c#commitcomment-2661417
remove uncommented railties boot_test.rb
Merge pull request #9352 from senny/remove_uncommented_boot_test

Remove commented railties boot_test.rb
Merge pull request #9348 from schuetzm/doc_no_indices_with_create_join_table

Add more documentation for create_join_table.
Rack::Test::UploadedFile is a permitted scalar
remove assigned but unused variable warning
Merge pull request #9357 from fabiokr/rack_test_uploaded_file

Rack::Test::UploadedFile is a permitted scalar
Merge pull request #9354 from NARKOZ/remove-warnings

remove assigned but unused variables
Update railties/lib/rails/application/configuration.rb

Changed comment that referenced the property #database_configuration_file, now it's paths["config/database"]
Update railties/lib/rails/application/configuration.rb

Better comment for database_configuration method
Merge pull request #9358 from iwiznia/patch-1

Update railties/lib/rails/application/configuration.rb
tweaks to the AP changelog [ci skip]
Remove not necessary changelog about time zone array mutation

This seemed to be introduced in master by
9dd64f2e0c1b3ce85b503b0f81c50c93f89ffbcd, so there's no need to add a
changelog entry for fixing it.

[ci skip]
Fix test name and refactor fake timezones creation in form options test
Use Array Difference to calculate the zones array, instead of iterating

It's faster, and doesn't force us to dup the timezones array.
Use #grep to filter priority zones when a regexp is given
determine the match shorthand target early.

Closes #7554.

This patch determines the `controller#action` directly
in the `match` method when the shorthand syntax is used.
this prevents problems with namespaces and scopes.
Use composition to figure out the forgery protection strategy