[DEPRECATED] PIM-1718 : remove flexible entity config and use doctrine meta

TODO 
 - [ ] rename pim_flexibleentity.flexible_config
 - [ ] delete src/Pim/Bundle/FlexibleEntityBundle/DependencyInjection/PimFlexibleEntityExtension.php and related configuration
 - [ ] fix product grids (group and variant)
 - [ ] update cookbook
 - [ ] avoid to inject whole container in flexible entity listeners (introduce a catalog context for locale and scope ?)
 - [ ] refactor TU
 - [ ] refactor icecat demo bundle

Bug fix: [yes|no]
Feature addition: [yes|no]
Backwards compatibility break: [yes|no]
Unit test passes: [yes|no]
Behat scenarios passes: [yes|no]
Checkstyle issues: [yes|no]*
ChangeLog updated: [yes|no]
Documentation PR: [link to the documentation PR if there is one]
Fixes the following jira: PIM-1718