Updated Changelog to reflect removal of :dependent => :restrict

Based on https://github.com/rails/rails/issues/2502, the option has
been removed.
Merge pull request #13699 from rystraum/dependent-restrict-removal

Updated Changelog to reflect removal of :dependent => :restrict
Only lookup `config.log_level` for stdlib `::Logger`. Closes #11665.

This prevents Rails from assigning meaningless log levels to third
party loggers like log4r. If `Rails.logger` is not `kind_of?(::Logger)`
we simply assign the `config.log_level` as is.

This bug was introduced by #11665.
removed extra comma [ci skip]
Merge pull request #13702 from kuldeepaggarwal/docs-fix

removed extra comma [ci skip]
Favor canonical environment variables for secrets

Prefixing an environment variable with `RAILS_` should be used when there is otherwise a conflict, such as `RAILS_ENV` or if it is being used for a very Rails specific value.

If we remove the prefix of `RAILS_` in the case of `RAILS_SECRET_KEY_BASE` then we can push for a pseudo standard among other frameworks that will accept a common environment key `SECRET_KEY_BASE` to keep your app secure. This is beneficial for containerized deployments such as docker, Heroku, etc. So that the container need to know one less thing about your app (it can just set it no-matter what language or framework you are using). 

This change also allows the defaults to be consistent with the way the secret key is accessed so `secrets.secret_key_base` is aliased to `SECRET_KEY_BASE` instead of `RAILS_SECRET_KEY_BASE`.
Merge pull request #13703 from schneems/schneems/rail-secrets-key

Favor canonical environment variables for secrets
revises a few things in the getting started guide [ci skip]

More to come.
"serie" => "series"
updates screenshot data [ci skip]
recover from test runs that leave the database in a bad state
Merge pull request #13704 from waynn/patch-4

"serie" => "series"
no need to to_sym
avoid more dynamic symbols