Simplified Model::mergeRow

This way a developer only needs to override setRow() to handle all fields
Uset relation when changing a model value
CS
Merge pull request #6308 from aschempp/pullrequests/model-mergeRow
Merge pull request #6307 from aschempp/pullrequests/model-relations
Fix some minor code formatting issues
Update Colorbox to version 1.4.31 (see #6309)
Simplify the "iflng" and "ifnlng" insert tags (see #6291)