Fixes #4324: removed old way of developing Yii from the docs since app/link is much better/simpler workflow

PS: should `start-looking-head.md` be `start-looking-ahead.md`? I remembered that is called look ahead.

Change git clone git@github.com:yiisoft/yii2-app-basic.git to 
git clone https://github.com/yiisoft/yii2-app-basic

- added german
- added @ links
- ordered languages by alphabet

```
vendor/bin/indent --spaces -r framework/
vendor/bin/indent --tabs -r . --pattern=*.json
vendor/bin/indent --spaces -r . --pattern=*.md
vendor/bin/indent --spaces -r . --pattern=yii.*.js
vendor/bin/indent --spaces -r . --pattern=*.css
```

fixes #2852

Added alternative way of setting up dev environment.