This is a proof-of-concept/prototype. It generates a Type and a Value class, as well as a fieldtypes.yml that registers the
fieldtype, but the class name, namespace, etc are still wrong.
Since the package isn't registered on packagist yet, you need to add a VCS entry to \ composer.json`:
Require the ezobject/wrapperbundle package into your composer.json file :
{
    "repositories": [
        { "type": "vcs", "url": "https://github.com/bdunogier/ez-fieldtype-generator-bundle.git" }
    ],
    "require": {
        "bdunogier": "dev-master"
    }
}
Add BDEzFieldTypeGeneratorBundle to EzPublishKernel.php:
$bundles = array(
    // ...
    new BD\EzFieldTypeGeneratorBundle\BDEzFieldTypeGeneratorBundle(),
);
php ezpublish/console generate:ez:fieldtype
When asked for the name of the bundle, use an existing bundle. If you don't have one for it, generate one using
generate:bundle first.
The script will then ask for the fieldtype's name, that is really the fieldtype's identifier.
Confirm generation, and the files will be written to the bundle:
$ php app/console generate:ez:fieldtype
  Welcome to the eZ FieldType generator
Your FieldType must be created in a bundle.
If you don't have a bundle for it, please create one using generate:bundle first
Target bundle name: BDTestBundle
A FieldType requires a unique identifier.
Identifiers can contain alphanumeric characters as well as underscores
FieldType name: bdtest
  Summary before generation
You are going to generate a "bdtest" FieldType in the "BDTestBundle" bundle.
Do you confirm generation [yes]?
Generating the FieldType code: OK