RFC: Unversioned bundle includes

[dantleech]

It would be beneficial to be able to register bundles only on a local installation, and not to have them in the versioned AbstractKernel class.

This is relevant for the DeveloperBundle which we do not (at least currently) want to include in the standard edition.

I propose that we conditionally include a file, e.g. bundles.local.php which returns adds bundles to the kernel. This file would be ignored in `.gitignore.

<?php
// bundles.local.php

return array(
    new Sulu\Bundle\DeveloperBundle()
);

This file will be included if it exists from the AbstractKernel.

[dantleech]

/cc @danrot @chirimoya @wachterjohannes @alexander-schranz

[danrot]

Sounds good to me.

[chirimoya]

https://github.com/sulu-io/sulu-standard/issues/621