create book module via dot-maker tutorial

[Jurj-Bogdan]

A few potential issues:

• especially compared to the API tutorial this one is quite a lot longer, should it maybe be split in multiple pages?
• a few code samples contain whole classes to make "copy-pasting" easier for readers, but i've left other classes out as only a few lines have to be included - problems are the imports, as readers might not know which class to import. Should i:
  • add full classes everywhere?
  • add fully qualified names for imports?
  • add the "use" statements in the code samples?

example for EditBookForm.php :

$this->add(
    (new Text('name'))
        ->setLabel('Name')
)->add(
    (new Text('author'))
        ->setLabel('Author')
)->add(
    (new Date('releaseDate'))
        ->setLabel('Release Date')
);

Also let me know of any typos or mistakes in general

Closes #17