Extract class for input option handling

There's a common pattern in here of:

``` php
$foo = $input->getOption('foo');
if ($foo) {
    return $foo;
}

// calculate foo some other way
return $foo;
```

This basic behavior could be easily encapsulated inside of a method like:

``` php
return $inputHelper->getOptionOrExec('foo', $functionToCalcFoo);
```
