Only set timestamps if timestamp is in pivot on existing pivots.
Merge branch '4.0'
Fix bug in query builder for caching. Fixes #1640.
Merge branch '4.0'
Add option to skip detach on sync.
Merge branch '4.0'
Fix a bug with selecting columns when accessing many to many relation.
Merge branch '4.0'
fix bug in belongs to many pagination.
Merge branch '4.0'