Updates reset_counters to allow counter name in params

cc https://github.com/rails/rails/issues/14848#issuecomment-41198795

Collected TimeZone's class methods together

Just moved class methods up in file and moved `def self.` methods into `class << self`.

Add missing tests for column type cast behavior

The fix introduced at 75ba7425 were
missing this case.

To fix the original issue mentioned at that commit the correct is to
remove update_config_files from the command list since we should not run
both config_files command when creating a new application.

Tests were added to make sure everything is working fine.

Fix app generator test hanging.

Fix symbol at guides getting_started.md

Ensure :js is defined regardless of the outcome of the test.

fixed capitalizations [ci skip]

jQuery, SQLite3 and Unicorn use these respective capitalizations pretty much everywhere else in the comment sections of the project.

Fix typo in CHANGELOG entry for #15071

Add support for counter name to be passed as parameter
on `CounterCache::ClassMethods#reset_counters`. This is
to be consistent with the other methods in the module
that all accept counter name.

Replace first person point of view on guides.

[skip ci]

Fixed duplicate subscribers in ActiveSupport::Subscriber

Conflicts:
	activesupport/CHANGELOG.md

Fix `Relation#delete_all` inconsistency

We were generating this configuration with :json what may break
applications upgrating from Rails 4.0-.

Now we always generate with a safer value and people is free to choose
hybrid if they want.

We don't generate with hybrid by default because there are some cases
that can fail. These cases are explained on the upgrading guide.

Closes #15141.

Remove unecessary require

Remove the assignment for real this time.

cc:
https://github.com/rails/rails/commit/a11e2fcff8cdc9691b977d8330abe63024f8c732#commitcomment-6353614
and 0369dbfd

We are using that code path in only one place so we should not add a
conditional to all the other cases. This will avoid performance
regressions on the old paths.

Small refactoring on clear_transaction_record_state

Remove code related to adapter which are no longer in repo