Added `yii\i18n\Formatter::intlCurrencySymbol`
Renamed Formatter::intlCurrencySymbol to currencySymbol
Fixes typo
 Added comment about $currency when it is null
changelog
Renamed `Formatter::currencySymbol` to `currencyCode`
Changelog
Fixes typo
Adjusted changelog
Adjusted documentation
Merge branch 'patch-1' of github.com:leandrogehlen/yii2 into leandrogehlen-patch-1

Conflicts:
	framework/CHANGELOG.md
Merge branch 'leandrogehlen-patch-1'