PIM-2484: Implements filtering by empty value for text
PIM-2483: Implements filtering for number
PIM-2488: Remove useless null fields
PIM-2441: Allow to filter on empty values for MongoDB
PIM-2441: Update oro platform used
PIM-2441: Update CHANGELOG
PIM-2441: Update UPGRADE-1.2.md file
MongoDB implementation has changed removing null values in NormalizedData field
PIM-2441: Inverse condition test
M-2441: Inverse condition test
Merge pull request #1036 from akeneo/PIM-2441

PIM-2441: Filter by empty values (Text and Number)