[ContentBundle,WebBundle] Improve ContentBundle to use the power of Symfony-CMF

| Q             | A
| ------------- | ---
| Bug fix?      | [yes]
| New feature?  | [yes]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| Fixed tickets | #1577 #1708 and maybe more
| License       | MIT
| Doc PR        | 

Added possibility to add from backend :
- menus, 
- slideshow (with liipImagine filter), 
- routes to static content,

![menu-content](https://cloud.githubusercontent.com/assets/1230954/4484282/cccdfefa-49b9-11e4-9e0d-89f456ab4ad6.jpg)

##### Added 3 slideshow location in layout with full backend edition. 

3 liipImagine filters created to generate images on the fly
- slideshow_small               260x200
- slideshow_medium          850x300
- slideshow_large               1170x380

![slideshow-backend](https://cloud.githubusercontent.com/assets/1230954/4484292/fbdfe0be-49b9-11e4-838d-17bb813dfb40.jpg)

##### Display slideshow in top, content and sidebar positions with sonata_block_render.
To test the rendering, you should create the 3 following slideshow
![slide-test](https://cloud.githubusercontent.com/assets/1230954/4484604/951f60da-49bd-11e4-9c71-15e30c5719ca.jpg)

##### Preview

Full width on top of sidebar & content
![home-slide-full](https://cloud.githubusercontent.com/assets/1230954/4484307/14a1cbee-49ba-11e4-8a9e-d8a39720c2ba.jpg)

Content top
![home-slide](https://cloud.githubusercontent.com/assets/1230954/4484299/0d7ae49a-49ba-11e4-934d-498f04d04613.jpg)

Sidebar bottom
![home-slide-sidebar](https://cloud.githubusercontent.com/assets/1230954/4484309/1919a534-49ba-11e4-939f-5af4e155c1e5.jpg)

##### Menus could be displayed in frontend by simply calling knp_menu_render and menu name (eg: {{ knp_menu_render('main') }})

![menu-backend](https://cloud.githubusercontent.com/assets/1230954/4484319/2ecff63a-49ba-11e4-8df1-2abd235ca95a.jpg)

##### Full route creation support to link static content .

Name is the final URL to acces te selected content (direct link by clicking View button)

![route-backend](https://cloud.githubusercontent.com/assets/1230954/4484334/4f4a2b06-49ba-11e4-8ec8-c2bf0159ea3b.jpg)

###### Route form edition

![route-backend-edit](https://cloud.githubusercontent.com/assets/1230954/4484337/51bbba1c-49ba-11e4-9a05-749228058db9.jpg)

Fixed some typos from previous ContentBundle commit, and create all translations strings

Reorganize route and template by grouping them in a content dir for better future maintenance

After @pjedrzejewski ContentBundle publication 2 days ago, here is a step forward to provide a decent CMS system to Sylius :)

Fully tested and working.
Not completely CSS styled but working at all.

Two problems remains :
- I don't know how to create the root node /cms/routes if it doesn't exists. All the others nodes are correctly created with doctrine:phpcr:repository:init command (don't forget to use it to generate the base nodes)
- There seems to be a limitation -> https://github.com/symfony-cmf/MediaBundle/issues/9 with the mediaBundle to override existing slideshow images (you should change filter from a position, save, and come back to the good filter and save again)

@pjedrzejewski : still waiting the collection fix to delete menu nodes and slides ;)

Awaiting your remarks
;)

Yeah, pure Symfony way is better, but I am fine with adjusting this in a future PR.