Feature/array property transformer

Bug fix: [no]
Feature addition: [yes]
Backwards compatibility break: [no]
Unit test passes: [yes]
Specs passes: [yes]
Replaced unit test classes removed: [no]
Behat scenario passes: [yes]
Checkstyle issues: [no]*
ChangeLog updated: [yes]
Documentation PR: [link to the documentation PR if there is one]
Fixes the following jira:

This PR enables the importation of doctrine array properties from flat files. It is notably necessary for importing conversion measure units in channels.