Implement EZP-23288: Allow to set modifier of Content Versions
Implement EZP-23288: Allow to set modifier of ContentTypeDraft

Avoids having to do an additional update to set creator before returning,
also makes it possible to pass user in case inner layers are uaware of
current user.
Merge pull request #966 from ezsystems/api_modifier

Implement EZP-23288: Allow to set modifier of Content Versions & ContentType
Fixed: EZP-23313 Yaml ParseException after symfony udpate to 2.3.19
Merge pull request #976 from crevillo/EZP-23313

Fixed: EZP-23313 Yaml ParseException after symfony udpate to 2.3.19