[Console] Fixed unsetting of setted attributes on OutputFormatterStyle

Unset only previous setted styles in place of all styles, before this fix,
OutputFormatterStyle reset all attributes with '\e[0m' sequence.
Now, if a foreground is setted, reset only the foreground so you can use innested attributes

Conflicts:
	src/Symfony/Component/Console/Tests/Formatter/OutputFormatterStyleTest.php
	src/Symfony/Component/Console/Tests/Formatter/OutputFormatterTest.php
	src/Symfony/Component/Console/Tests/Output/OutputTest.php