Prepare to replace by form- and twig- extensions

[wbloszyk]

Feature Request

CoreBundle was split to *-extensions and abandoned but not provide easy way to update this change in existing project. User must instant replace this bundles and all using service also upgrade all sonata dependencies at the same time but should have possibility to do it step by step.

Summary of the feature.

CoreBundle should drop form and twig directory and required extensions 0.x created from this directory. Also extensions 0.x should include configuration from extensions 1.x. This will allow drop CoreBundle deprecations and allow use extensions 0.x instead CoreBundle. Upgrade extensions will be easy to.

Three change are required:

• prepare form extensions
  • [x] create form-extensions 0.x - https://github.com/sonata-project/form-extensions/pull/79
  • [ ] release stable form-extensions 0.1
• prepare twig extensions
  • [x] create twig-extensions 0.x - https://github.com/sonata-project/twig-extensions/pull/74
  • [ ] release stable twig-extensions 0.1
• [ ] replace form and twig directories by standalone extensions - #736

[wbloszyk]

I create first working demo. Tomorrow I will check it againg.

Sonata packages

$ composer show 'sonata-project/*'
sonata-project/admin-bundle        dev-master 379a0e0 The missing Symfony Admin Generator
sonata-project/block-bundle        3.18.4             Symfony SonataBlockBundle
sonata-project/cache               2.x-dev 4c857d7    Cache library
sonata-project/core-bundle         3.x-dev 5f222dd    Symfony SonataCoreBundle (abandoned)
sonata-project/doctrine-extensions 1.x-dev e5da38c    Doctrine2 behavioral extensions
sonata-project/exporter            2.x-dev 21e02ad    Lightweight Exporter library
sonata-project/form-extensions     0.x-dev c115b38    Symfony form extensions
sonata-project/twig-extensions     0.x-dev ba75b23    Sonata twig extensions

[wbloszyk]

Move it to #741