Changing UcmContent to use the new storage format for FieldMapping. Checking if it's stored as object or array->object.
Inserting new storage format for FieldMappings during install.
Updating fieldmappings in database during update
Updating unit tests
Merge pull request #1398 from Bakual/FieldMappings3.1.2(2)

Removing the array part in field_mappings