Tabs to spaces to be consistent

```
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 #3542: Removed requirement to specify `extensions` in application config
Mail layout charset specification fixed
Missing $message var reference removed from mail layouts
added explicit comment about file transport to mail config

fixes #3694
basic application template tests adjusted
basic application template fixtures added
Fix .gitignore for `basic` and `advanced` application templates
Merge remote-tracking branch 'upstream/master'

Conflicts:
	config/console.php
	config/web.php