Merge branch 'hotfix/3.0.3'
Merge branch 'release/4.0.0'
Fixed the filters HTML markup in Model\Relations
Fixed a bug in the relations that purged data on every save_callback
Convert optgroups so they work with FormSelectMenu
Fixed options converter
Fixed weight calculation
Deleted CHANGELOG, there's a GIT history anyway
Merge branch 'hotfix/4.0.1' into develop