Merge pull request #11747 from bradly/guides_getting_started_fix

Add note that you must be in the rails app when starting the server
No need to abbreviate application

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Merge pull request #11737 from tkhr/fix-document-about-on-validation-helpers

Fix active_record_validations.md document, `:save` for `on:` validation helper was never available
Conflicts:
	guides/source/active_record_validations.md

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Remove "Using Action View outside of Rails" section from AV overview guide

The section was clearly wrong and was just an example about how to use ActiveSupport helpers in Rack/Sinatra

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