Rename the 'data' property of Version to 'snapshot' for clarity
Also rename some methods in VersionBuilder
Add setters in Version for nullable fields
Store the username of the author inside the Version entity
Fixes Completeness accumulation and wrong selection of products
Refactor of completeness generation in MongoDB
Manage full completeness generation
Merge branch 'master' into mongodb/completeness_perfs
Revert changes on normalization
Use prices requirement into required count
Merge branch 'master' into PIM-2448
Merge branch 'master' into PIM-2448

Conflicts:
	spec/Pim/Bundle/VersioningBundle/EventListener/AddUserListenerSpec.php
Add 'pending' property to Version entity
Merge branch 'master' into PIM-2448
Merge branch 'master' into PIM-2448
Merge branch 'master' into PIM-2448
Replace Pending with Version

Normalized modifications made to the versionable entities are stored in the changeset property.
The real changeset and snapshot are calculated later by the refresh command.
Effectively, pending versions are not created if the provided snapshot is empty.
Improve VersionBuilderSpec
Merge branch 'master' into PIM-2448
Allow building multiple pending versions
Remove unused images and assign orphaned images