Add possibility to configure wrapping length of Dumper-class

[duxthefux]

Please see #45

To add the possibility of "wrap always", it will be necessary to add public static variable $wrapAlways into the Dumper class and use it here https://github.com/nette/php-generator/blame/master/src/PhpGenerator/Dumper.php#L115

[dg]

Printer has new property $wrapLength