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.

fixes #1606

no need to download codeception via composer when phar is used.
fixes #1913

[SK] Added translation.

* '1818-gii-excess-forms' of https://github.com/johonunu/yii2:
  using camelcase
  changed vars
  Gii excess forms. Fixes #1818

Added sticky futter. Fixes #1822

* '1907-sr-language' of https://github.com/johonunu/yii2:
  rearanged language array
  remove sr-cyrl, it's the same as sr
  Serbian translation. Fixes #1907

Conflicts:
	framework/messages/config.php