Show warning alerts at frontend
Multiple object managers support
minor touches
remove unused use statement
[ContentBundle,WebBundle] Improve ContentBundle to use the power of
Symfony-CMF

Added possibility to add from backend :
- menus, 
- slideshow (with liipImagine filter), 
- routes to static content,

Added 3 slideshow location in layout. Display slideshow in top, content
and sidebar positions with sonata_block_render.

Menus could be displayed in frontend by simply calling knp_menu_render
and menu name (eg: {{ knp_menu_render('main') }})

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
[ContentBundle,WebBundle] Fix some standard coding for PR 1962
[ContentBundle,WebBundle] Fix some bad coding practices while displaying
collection for slideshow and menu
[Core] Optimize NthOrder promotion checker.
[WebBundle] Adjust sidebar menu to better look at smaller screens
Add missing translations
Fix schema
Merge pull request #1969 from umpirsky/fix/schema-cascade

Fix schema
Merge pull request #1968 from stloyd/bugfix/backend_menu

[WebBundle] Adjust sidebar menu to better look at smaller screens
[ResourceBundle] Don't use query walkers when pagination is called

This i.e. for product pagination removes one query run on whole table without index usage (you can guess how terrible it is when database have 90k products/variants).
Fix user check in PromotionEligibilityChecker
Merge pull request #1972 from stloyd/bugfix/pagination_count

[ResourceBundle] Don't use query walkers when pagination is called
Merge pull request #1974 from umpirsky/fix/promotion-checker

Fix user check in PromotionEligibilityChecker
Merge pull request #1967 from stloyd/bugfix/nth_order

[Core] Optimize NthOrder promotion checker.
Fix-1981
Latest fix for ContentBundle
Merge pull request #1990 from Joypricecorp/fix-1981

[ContentBundle] Fix-1981