add a menu helper

[mhor]

[javiertrejo]

@mhor, if you tell me what is a menu helper, may be can i help you with this enhncement

[mhor]

@javiertrejo mediainfo command can return in certain information about menu like this.

As it this information are not usable. The goal of the issue is to add some function to make information about menu revelant.

For example:

$chapters = $menu->getChapters();
$chapter = reset($chapters);
print_r($chapter->getStart()); 
print_r($chapter->getEnd()); 
print_r($chapter->getDuration()); 
print_r($chapter->getName());
print_r($chapter->getLang());
// ....