Symfony 3 updates

Update bundle with commits from apy/datagrid-bundle 's master branch.

Bug Fix

Name	Description
Documentation	Fixed display bugs for some tables in Export section.

Other changes

• Merge last commits from APY/DataGridBundle's master branch.

Symfony 3 compatibility

This release is starting point for Symfony 3 compatibility.

Bug Fix

Name	Description
Twig	Update Twig Extension deprecated calls to initEnvironment
Service declaration	Change scope="prototype" to shared="false"

Other changes

• Reorganization of documentation.
• Merge last commits from APY/DataGridBundle