PIM-3209: Fix import running even with wrong file

*Added verification of the file extention before the launch of the job
*Added new behats in order to verify that the file extention is allowed or not
Merge pull request #1695 from akeneo/PIM-3209

PIM-3209: Import is running when we use upload and import with a file with wrong extension
PIM-3234 Uses category ids to filter products
PIM-3234 Fixes unclassified category filter
PIM-3234 Changelog on bugfix
PIM-3234 : extract method to ease override
Merge pull request #1697 from akeneo/PIM-3234

PIM-3234 Fixes category performance filter problem
Prepare v1.2.10
[CrowdIn] Updated translations
PIM-3308: fix unclassified filter
Merge pull request #1709 from akeneo/PIM-3308-stable

PIM-3308: fix unclassified filter
Format date for grid date cells on the server side
PIM-3308: fix unclassified filter
Merge pull request #1713 from akeneo/PIM-3308-stable

PIM-3308: fix unclassified filter
Merge pull request #1707 from nono-akeneo/crowdin/1.2-2014-10-27-04-00

Update translations from CrowdIn
PIM-3311: add Behat scenarios to cover the bug of creation of products with missing identifier during imports
PIM-3311: fix creation of products with missing identifier during imports
Merge pull request #1719 from akeneo/PIM-3311-stable

PIM-3311: fix creation of products with missing identifier during imports
PIM-3312: check attributes locales, channels and currencies in CSV header during imports
PIM-3312: avoid BC breaks