bug with variable widget_type

Variable “widget_type” does not exist in SonataAdminBundle:Form:filter_admin_fields.html.twig
* http://stackoverflow.com/questions/23004015/variable-widget-type-does-not-exist-in-sonataadminbundleformfilter-admin-fie

* http://stackoverflow.com/questions/22985378/sonata-admin-filters-should-looks-like-set-of-checkboxes-but-got-error
Fix form_type option in date filter types
Merge pull request #2136 from Bladrak/dateFormType

Fix form_type option in date filter types
Added datepicker assets to default configuration
Merge pull request #2137 from Bladrak/dpAssets

Added datepicker assets to default configuration
added documentation
Ensure that forms render properly withouth MopaBootstrap
Merge pull request #2138 from Bladrak/mopaCp

Ensure that forms render properly withouth MopaBootstrap
Expand the group that contains the active menu item
Fixed wrong assets paths
Merge pull request #2144 from Bladrak/assetsPath

Fixed wrong assets paths
Merge pull request #2143 from patrickli/expand-active-menu

Expand the group that contains the active menu item
Always add 'form-control' class to select boxes
Fixed typos
Merge pull request #2149 from pborreli/typos-19

Fixed typos
ListMapper::addIdentifier() working when user is only granetd for "VIEW" action.
Merge pull request #2168 from phansys/master

ListMapper::addIdentifier() working when user is only granted for "VIEW"
Update composer.json

Update twig requirement to 1.15 to support round filter used in https://github.com/sonata-project/SonataAdminBundle/blob/453c87199286d30f4918a06a2665ecbc7ed1e2b6/Resources/views/Core/add_block.html.twig#L3
Merge pull request #2170 from lucasgranberg/patch-1

Update composer.json
Fix create_button.html.twig for subclass

Button group in dropdown is not a good idea ;)
Instead add an item for each subclass grouped by divider