Create.js integration and ContentBundle

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Very rough initial version of ContentBundle. Summary of what is started and what is the goal:

- Integrating the awesome create.js for inline editing, currently only the PHPCR content, in future also products. (but I plan to use PHPCR for product page contents management)
- Menus management via CMF, stored in PHPCR.
- Routes and RedirectRoutes management.
- More block types.

I did not want to clutter the CoreBundle with all this new stuff, so I decided that best way is not introduce separate bundle. Also, if you do not need the CMS functionality, you can remove it and be happy.

PHPCR with SonataBlockBundle (CmfBlockBundle) is reaaally powerful and cool. Some ideas for future blocks we can introduce:

- ProductBlock
- TaxonomyBlock

And also the TaxonomyMenuNode, which will generate all menu nodes from the Taxonomy taxon's.
Blocks or these menus will be put in Page slots, determined by the layout. With theming it will be pretty cool! Still a lot of work though, I will prepare todo list soon.

For sure it will be greatly improved after #1488 is merged. (create.js part)

![sylius - modern ecommerce for symfony2 - google chrome_026](https://cloud.githubusercontent.com/assets/614970/2937499/5a743b92-d8aa-11e3-8ebe-6c213d7931f2.png)