Updated extension docs to be less restrictive about choosing namespace, more neutral composer.json example

Fixes #1937: Fixed wrong behavior or advanced app's `init --env` when called without parameter actually specified

Fixed missing danish translation

Fixed missing translation

fixes #1913

Update extensions.md, Namespace section

workflow.md: fixed invalid upstream url

Make clear that "type" in extensions' namespaces must be in plural form (widgets/behaviors/modules)

Fixes #1894: The path aliases `@webroot` and `@web` are now available right after the application is initialized

Translation for Portuguese (pt-PT, Portugal).

fixed Markdown::process() to make it compatible with parent declaration.

Adapted from Portuguese Brazilian translation.